The Collaborative International Dictionary of English v.0.48:

Goober \Goo"ber\, n.
   A peanut. [Southern U. S.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Peanut \Pea"nut\ (p[=e]"n[u^]t), n. (Bot.)
   The fruit of a trailing leguminous plant (Arachis
   hypog[ae]a); also, the plant itself, which is widely
   cultivated for its fruit.
   [1913 Webster]

   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.
         [1913 Webster]

WordNet (r) 3.0 (2006):

goober
    n 1: pod of the peanut vine containing usually 2 nuts or seeds;
         `groundnut' and `monkey nut' are British terms [syn:
         peanut, earthnut, goober, goober pea, groundnut,
         monkey nut]