Search Result for "running back":
Wordnet 3.0

NOUN (1)

1. (football) a back on the offensive team (a fullback or halfback) who tries to advance the ball by carrying it on plays from the line of scrimmage; 



WordNet (r) 3.0 (2006):

running back
    n 1: (football) a back on the offensive team (a fullback or
         halfback) who tries to advance the ball by carrying it on
         plays from the line of scrimmage