Webster's Revised Unabridged Dictionary · 1913

Panic

Panic , noun

[Latin panicum.]

(Botany) A plant of the genus Panicum; panic grass; also, the edible grain of some species of panic grass.
Collocations (1)
Panic grass (Botany) , any grass of the genus Panicum.

Panic , adjective

[Greek paniko`s of or pertaining to Pa`n Pan, to whom the causing of sudden fright was ascribed: compare French panique.]

Extreme or sudden and causeless; unreasonable; -- said of fear or fright; as, panic fear, terror, alarm.
A panic fright. — Dryden

Panic , noun

[Greek to~ paniko`n (with or without dei^ma fear): compare French panique. See Panic, a.]

1.
A sudden, overpowering fright; esp., a sudden and groundless fright; terror inspired by a trifling cause or a misapprehension of danger; as, the troops were seized with a panic; they fled in a panic.
2.
By extension: A sudden widespread fright or apprehension concerning financial affairs.