Like "stop" and "quit" in the above examples, basta is the imperative (command, order) of a verb, but not a verb meaning "to stop" or "to quit." The regular first conjugation verb bastare means "to suffice, to be enough." Thus, when you are shouting basta! to someone, you are saying "that's enough!" The French say the same thing when they exclaim ca suffit!
The verb is used in other ways, of course. In its most common meaning:
I soldi non bastano mai.
There's never enough money.
Basta cosi'? (often said while offering food or drink)
Is that enough?
Idiomatically, it can mean "as long as" or "all it takes."
Va bene se viene da noi, basta che non resti a cena. (notice the subjunctive)
It's all right if he comes to our house, as long as he doesn't stay for dinner.
Ma che ci vuole? Basta un po' di buona volonta'!
It doesn't take much; it just takes some will-power!
