1. 
1. 
[syn: offside, offsides]
ADVERB (1)
1.  illegally in advance of the ball or puck; 
The Collaborative International Dictionary of English v.0.48:
offside \offside\ offsides \offsides\adj. (Sports)
   Illegally beyond a prescribed line or area or ahead of the
   ball or puck; -- in sports such as football or hockey; as,
   the touchdown was nullified because the left tackle was
   offside.
   [WordNet 1.5]
WordNet (r) 3.0 (2006):
offside
    adv 1: illegally in advance of the ball or puck
    adj 1: illegally beyond a prescribed line or area or ahead of
           the ball or puck; "the touchdown was nullified because
           the left tackle was offside" [syn: offside, offsides]
           [ant: onside]
    n 1: (sport) the mistake of occupying an illegal position on the
         playing field (in football, soccer, ice hockey, field
         hockey, etc.)