"Big cat" is a colloquial term used to describe the four largest wild cats in the Felidae family: lions, tigers, jaguars, and leopards. It is not a scientific or biological term.

Because it is not a biologically defined term we may need to incorporate multiple information trying to define it. Adding to Peter Donkor 's above answer, we may need to try and define the term "four largest wild cats". I suggest considering all cats (felids) with weight more than 20Kg, a used criteria in literally works such as Santos et al., (2022) contrary to the smaller ones that are define by Curveira-Santos et al., (2021) as mesopredators. A case of which we can include with them the cheetah (Acinonyx jubatus).

I think that this is a good criterion to use in order to define the four largest wild cats. It is important to consider the weight of the cats in order to differentiate between the larger cats and the smaller cats. This criteria also allows us to include the cheetah in the group of the largest wild cats.

Comments of Wilflide Institue of India, Peter Donkor &Thobias Tomeka are sufficient for this. There are many such terms in common/vernacular languages which can confound or even confuse new learners. They should not be adopted as scientific terms till they are verified by proper experts of the field. For example, Bisons of north america are called buffaloes though they are from a different genus altogether. There must be many others too, they should be considered local terms and not considered for any scientific discussions.

i think this definition is according to the size

and this is similar to naming the ostrich from a commercial point of view with Red-necked, Blue-necked and Black-necked ostriches@

"Big cat" is any cat that is large and charismatic enough to raise big money, thus skewing conservation action in the favor of those who work on them.

A "big cat" is a common term used to refer to any of the large, carnivorous felids (members of the cat family) found in various parts of the world. It is not a scientific or biological term, but rather a colloquial term used to describe these animals. Some examples of big cats include lions, tigers, jaguars, leopards, and cougars. These animals are generally characterized by their large size, powerful muscles, and sharp claws and teeth, which they use to hunt and kill prey.

In scientific terms, the term "big cat" is not used because it is not a taxonomically or biologically meaningful category. Instead, scientists classify these animals based on their evolutionary relationships, using scientific names and taxonomic classification systems to group them into specific genera and species. For example, lions, tigers, and jaguars are all members of the genus Panthera, while leopards and cougars belong to the genus Puma.