Cat - A domesticated member of the species Felis catus.
Stray - A cat who had a home but is now abandonned
Feral - A cat who has grown up without a home, in the streets. Can be fearful of humans.
Kitty - Another term for a cat, of any age.
Fluffy - Fur that is thick, or airy. Or just the trait of having fur.
Floof - Fluffy, but even more so.
Smol - Small, but in an adorable manner.
Chonker - Not exclusive to cats. A cat that is fat, or just very large.
Beans - the pawpads, particularly the toes, of a cat. Extra points if they're pink.
Blep - When a cat sticks out their tongue and forgets it put it back in. :P
Mlem - A cats tongue over it's nose.
Doot - A cat gait that's not a run, but faster than usual walking. Has a bit of a bounce.
Teefsies/fangs/snaggleteef - The canine teeth of a cat, particularly when they are sticking out of a closed mouth.
Wigglebutt - The action cats take before pouncing, of swaying their behinds and body.
Bottlebrush/poof - When a cat is startled or afraid, and it's tail fur puffs up to make it appear larger.
Plop - The act of a cat going from standing to suddenly lying on their side. Dropping onto the floor.
Kneading/making biscuits/Squeeging - A rhythmic pushing of the paws into a soft surface, often pushing the claws into it also. Usually accompanied by purring. Made when cats are getting comfortable, and are happy.
Cattaps - When a cat taps an object for attention.
Zoomies - When cats suddenly, without warning, get very excited and start sprinting around and playing.
(cat)Loaf - A way of lying. With paws underneath, tail curled around, and body in a straight line, the cat often looks like a loaf of bread.
(cat)Bun - Another way of lying. On their side, curled into a perfect circle.
(cat)Baguette - Another way of lying down. Stretched out, with legs tucked underneath, and head down.
Purrito - a cat or kitten wrapped in a blanket or towel so that only their head is poking out.
Boop - Briefly touching a cat with a single finger, usually on the nose.