Panic

1 *a : a sudden overpowering fright; also : acute extreme anxiety b : a sudden unreasoning terror often accompanied by mass flight c : a sudden widespread fright concerning financial affairs that results in hurried selling and a sharp fall in prices
2 slang : one that is very funny

Example sentence:
Jennifer experienced a sudden panic at the thought of failing all of her classes.

Did you know?
"Panic" comes to us from French "panique," which in turn derives from Greek "panikos," meaning literally "of Pan." Pan is the pipe-playing, nymph-chasing Greek god of fertility, pastures, flocks, and shepherds. (His name is a Doric contraction of "paon," meaning "pasturer.") He also has a rather dark side — his shout is said to have instilled fear in the giants fighting the gods, and the Greeks believed him responsible for causing the Persians to flee in terror at the battle of Marathon. "Panic" entered our language first as an adjective suggesting the mental or emotional state that Pan was said to induce. The adjective first appeared in print at the beginning of the 17th century, and the noun followed about a century later.