Are cheetahs big cats? No they are not. In terms of size they are big but someone decided that the term ‘big cats’ referred to the four roaring cats of the genus Panthera, namely, tiger, lion, jaguar and leopard. Controversially someone decided to include the snow leopard in this distinguished group but the snow leopard does not roar and in my view is a different kind of cat. The snow leopard is relatively friendly towards humans unlike the roaring cats.
The term ‘big cat’ loosely refers to size but it is not exact because on my assessment the top four largest wild cat species are in descending order: tiger, lion, jaguar and puma. The leopard is fifth. But the puma does not roar either and is also quite retiring like the snow leopard.
I don’t have much more to say in response to the question: are cheetahs big cats? I have a page on the tiger roar which explains the anatomical reasons behind this vocalisation.
Gustav Peters says that the tiger roar is not a true roar! That puts the cat among the pigeons. By the way that phrase comes from the time when caracals hunted with potentates in India and they’d see how many pigeons a caracal could catch! If Gustav is correct we could say that the tiger roar is different to those of the lion, jaguar and leopard. Not that we would notice.
Meow and Purr
The tiger does not purr but has his/her own version of the meow. The tiger has an extensive range of vocalizations. Read about them by clicking on this link.
Wozencraft mapped out the Panthera lineage. It includes the four big cats plus the clouded leopard and snow leopard. The important point is that the classification of the wild cat species is not entirely settled. The ‘clouded leopard was the first to diverge from the ancestral line, followed by the snow leopard. The last group of the four big cats diverged very recently, an estimated 2-3 million years ago‘ (Wild Cats of the World page 15).