Peanut \Pea"nut\, n. (Bot.) The fruit of a trailing leguminous plant (Arachis hypog[ae]a); also, the plant itself, which is widely cultivated for its fruit.

Note: The fruit is a hard pod, usually containing two or three seeds, sometimes but one, which ripen beneath the soil. Called also earthnut, groundnut, and goober.

Source: Webster's Revised Unabridged Dictionary (1913)