I would tell a child that a computing is a process done by a computer.

Computing has the following general meanings:

"calculate or reckon (a figure or amount).

"we can compute the exact increase"

synonyms: calculate, work out, reckon, determine, evaluate, quantify; More

make a calculation, especially using a computer.

"modern circuitry can compute faster than any chess player"

(But wait a minute, I don't have to tell that to a child, because children are born into homes where computers are already present.  I just say that is what that machine in the corner does..)

I would tell a child that a computing is a process done by a computer.

Computing has the following general meanings:

"calculate or reckon (a figure or amount).

"we can compute the exact increase"

synonyms: calculate, work out, reckon, determine, evaluate, quantify; More

make a calculation, especially using a computer.

"modern circuitry can compute faster than any chess player"

(But wait a minute, I don't have to tell that to a child, because children are born into homes where computers are already present.  I just say that is what that machine in the corner does..)

In addition to what Miranda Yeoh present, computing is the study, field of computers and computer programming. Thanks for sharing your question with me. 

Wikipedia describes computing as:

Any goal-oriented activity requiring, benefiting from, or creating algorithmic processes—e.g. through computers. It includes designing, developing and building hardware and software systems; processing, structuring, and managing various kinds of information; doing scientific research on and with computers; making computer systems behave intelligently; and creating and using communications and entertainment media.

Attached are some articles on computing:

Computing means any goal-oriented activity requiring, benefiting from, or creating computers

Yes , the term " calculating " is  in conjunction to the computer, especially in the last decade, when calculations become enormous and the computer can  solved in a short period of time.

Computing deals with various activities and it is part of various devices such as mobile phones, notebooks, cameras, IoT, etc.

Even networks use computing. 

Dear Dr. Qasim,

Computing has become a verb that represents the operations performed by a computer. The word itself was used since 1800s with the meaning of making sense. When computer was invented, the word usage increased and become what is mentioned in the first sentence of this answer. 

Thanks for the question. 

Dear Colleagues,

Good Day,

"The process of utilizing computer technology to complete a task. Computing may involve computer hardware and/or software, but must involve some form of a computer system. Most individuals use some form of computing every day whether they realize it or not. Swiping a debit card, sending an email, or using a cell phone can all be considered forms of computing. "Mason understood that his new job at the large IT firm would require a large portion of computing projects."

http://math.stackexchange.com/questions/424693/whats-the-meaning-of-computing-an-integral-at-a-given-point

“Man is a slow, sloppy, and brilliant thinker; computers are fast, accurate, and stupid.”

                    ― John Pfeiffer

Dear Colleagues,

Good Day,

DEFINITION OF COMPUTING

• the branch of engineering science that studies (with the aid of computers) computable processes and structures.
• the procedure of calculating; determining something by mathematical or logical methods.

Dear Hazim

Computing is used to deal with all materiel or activities using computer, practical or theoretical.

·         computing includes designing and building hardware and software systems for a wide range of purposes; processing, structuring, and managing various kinds of information; doing scientific studies using computers; making computer systems behave intelligently; creating and using communications and entertainment media; finding and gathering information relevant to any particular purpose, etc

@ Kausel

Yes, but The performance calculations need a powerful compilator.

Any work done with the help of processor and perform meanigfullcalculations 

 If we define this item in simple way we can say that computing means to calculate, work out, evaluate, quantify; designing  using a computer.

I saw the computer, for the first time in my life, in the year 1975. It was a huge machine which occupied a complete room & its function was just computing which meant calculating only at that time. After 4 years, I used the "punching cards" as MSc student in the U.K. to get graphs out of the computer (which occupied half a room). It became bifunctional for me (calculate & plot). I remeber when the IBM PC sets (Pentuim One) first arrived to my present university in the mid 1980s. At once, they caught my attention & a friend taught me how to operate a PC. In 1995, the internet came to my country. The PC, since then, has become versatile multifunctional but it is not easy to change its original name.

Computing usually refers to doing or calculating information/data that are digital or numeric and hence the name computer contrary to thinking what we humans do consciously and hence the name thinker although we do computing as well. 

We humans compute consciously while computer do mechanically. Th computations to identify vibrant colors of flowers by digital codes that  computers do  and the one made by humans by actually seeing the colors and the feelings associated with them  are both computations but the latter is of consciousness.

All living things in nature compute, plants either in desert, temperate or cold places compute the amount of sunshine they need for a proper photosynthesis to happen by determining the shapes and sizes of their petals or leaves.  Falcons compute to determine the fastest path or route to catch a prey from a lower position. Tigers and cheetahs compute their speed by properly controlling their motions and cancelling the sideways momentum by their tails in order to catch their prey in the wild jungle.

Therefore nature is one of the best commuting phenomena for optimal results.  

I think computing in computer context refers to processing & transformation of certain input / raw data into certain output / information / insight based on software logic & using certain hardware capability.

The process of utilizing computer technology to complete a task. Computing may involve computer hardware and/or software, but must involve some form of a computer system.

Most individuals use some form of computing every day whether they realize it or not.

Swiping a debit card, sending an email, or using a cell phone can all be considered forms of computing.

"Mason understood that his new job at the large IT firm would require a large portion of computing projects."

http://www.businessdictionary.com/definition/computing.html

https://en.wikipedia.org/wiki/Computing

Dear All

I mean in computing, the concept of computing on the computer, and not as a verb , work,  or action.

Dear all

Computing is the activity of using a computer and writing programs for it. About Computer application cannot be elucidated with a few words. We have the database application for example; it is being widely applied by bank, hospital, government, big and small firms almost everywhere. The application of the database is most important fundamental part in dynamic WEB application program.

Dear all

Following computer becomes more and more versatile; the meanings of computing are also increasing.

Computing is basically the study of how computers and computer systems work and how they are constructed and programmed.  Please check the following link.

http://www.computingbook.org/