Source : Webster's Revised Unabridged Dictionary (1913)

Protuberate \Pro*tu"ber*ate\, v. i. [L. protuberare; pro forward
   + tuber a hump, protuberance. See {Tuber}.]
   To swell, or be prominent, beyond the adjacent surface; to
   bulge out. --S. Sharp.

Source : WordNet®

protuberate
     v 1: cause to bulge out or project
     2: form a rounded prominence; "The starved child's belly
        protuberated"