Generally it could be defined as an ability or capacity of something to be maintained or to sustain itself. It's about taking what we need to live now, without jeopardising the potential for people in the future to meet their needs. If an activity is said to be sustainable, it should be able to continue forever.

Sustainable construction aims to meet present day needs for housing, working environments and infrastructure without compromising the ability of future generations to meet their own needs in times to come. It incorporates elements of economic efficiency, environmental performance and social responsibility – and contributes to the greatest extent when architectural quality, technical innovation and transferability are included. 

Sustainable construction involves issues such as the design and management of buildings; materials performance; construction technology and processes; energy and resource efficiency in building,  operation and maintenance; robust products and technologies; long-term monitoring; adherence to ethical standards; socially-viable environments; stakeholder participation; occupational health and safety and working conditions; innovative financing models; improvement to existing contextual conditions; interdependencies of landscape, infrastructure, urban fabric and architecture; flexibility in building use, function and change; and the dissemination of knowledge in related academic, technical and social contexts.

I would like to think sustainable building have something to do with construction of building structures to meet current needs without compromising potential needs for future generations. it is however very difficult to guess the tastes and preferences of future generations that nobody knows but I would like to believe that if we are to build sustainably, buildings have to be durable and should be able to serve needs for the future, coming generations.

Sustainable Buildings is a little bit of a misnomer.  If, as Abdul says above, Sustainability is the state where something (typically humans) can exist on the planet in perpetuity, then buildings are not able to be that.  Everything needs maintenance and will ultimately be removed and replaced. 

Individuals can not be Sustainable.  Communities, nations, countries, continents, and the planet as a whole can all be Sustainable, but not Buildings.  It is possible, though, to have a building that aids in the overall Sustainability of a community.  And in that sense, then yes, but only in that sense.

I would argue that Sustainability Engineering is the process of maximizing social benefit while minimizing negative ecological impacts.  Where energy use has negative ecological impacts, then reducing energy use would reduce those negative ecological impacts.  Maximizing social benefit is more difficult, requiring us to understand the needs of our community (as opposed to the wants) and the obstructions within the community that prevent individuals, families, and the community as a whole from having those needs met.  Engineers can't do that part of the analysis by themselves.  

LEED, or Envision, or CEQUAL make a stab at that analysis, based on a fairly sophisticated understanding of how urban development works, and it is likely to be meaningful in a lot of places (though, maybe not where you are doing your analysis).  TBL, by it's nature, will not produce maximal solutions (though near-optimal is certainly possible) that are independent of subjectivity, because you have to find trade-offs between the three pillars. 

I would suggest to provide the maximum social benefit in an undefined (and likely undefinable) future, we would want to design with the maximum resilience and adaptability.  Make sure it can be maintained without shutting down the whole structure.  Make sure you're using parts that we'll be able to replace in a low-carbon future.  Make sure you haven't traded away resilience for efficiency.  Make sure it is off-grid capable, so if the grid fails, you building doesn't have to.  Use what you get for free.  Keep energy as close to it's original form (thus storing heat and cold, and using lots of daylighting) as possible.  Make sure the building can be repurposed without demolition.  As so forth.  All of these things will let the community exist in perpetuity at a higher quality of life than would be possible without doing these things.

Sustainable building design and construction is the practice of creating structures and using processes that are environmentally responsible and resource efficient throughout the life cycle of a building– from selecting the site to design, construction, operation, maintenance, renovation, and finally, deconstruction. Sustainable building expands on and complements the classical building design considerations of economy, utility, durability, and comfort. Other terms for sustainable building include green building, high performance building, or sustainable or green construction.

a.  The Impact of Buildings on the Environment

According to the U.S. Environmental Protection Agency and the U.S. Green Building Council, construction and operation of all buildings in the United States result in the following consumption of resources:

72 percent of electricity resources

39 percent of total energy used

3 billion tons of raw materials annually (40 percent of raw stone, gravel, sand, and steel; 25 percent of virgin wood)

17 percent of freshwater flows

As well, construction and operation of all buildings in the United States result in the following generation of waste materials:

25-40 percent of municipal solid waste

50 percent of CFCs

30 percent of CO2 production

Other air emissions and water discharges

Given the extent to which buildings affect the environment, the opportunities for improvement through sustainable planning, design, construction, and operations and maintenance practices are significant.

I agree with Douglas Nuttall and Osama Abdelgawad, 

Sustainability and Sustainable building even if goes on a similar lines can not be discussed with the same definition as been given by bruntland commission. No doubt the long life buildings are necessity in today's context, but it may not be seen as a permanent solution as life and death are absolute truth of life - be it related to building. For human life NATURE is important for its survival. Artificial oxygen cylinders can not replace natural oxygen we are inhaling from nature. So It is important to make buildings in more eco frinedly manner, which will consume less energy and will left very low impact on the environment throughout its life span.

As architecture or building industry is a outcome of Economic and Social growth of the community, it affects every sector on this earth, so we need to see the sector in a global way and reduce the environmental impact of it throughout its existence- and the building which is outcome of all of the above factors could be called as sustainable building.