Ruminate.
A donkey is NOT a cud-chewing animal.
The times you see them chewing are when they are chewing their cud.
"To chew the cud" is "ruminer" "The cud" is "la panse" A cud-chewing animal is "un ruminant"
If you are asking why they call it that, it could be because some people look like like they are chewing their cud while they are chewing gum. Cud it regurgitated feed that the cow then rechews.
Ruminants
Yes.
No. Zebra are close cousins to horses, which are not cud-chewing animals because none of them have four chambers in their stomachs; just one simple stomach.
A lump of chewing tobacco is called a quid. A variant of the word: cud quid - (noun) a lump of chewing tobacco
Cud. Cows regergitate grass and it is call cud. Hence cows chew their cud.
Alpaca
Ruminant