Wordnet 3.0
NOUN (1)
1. 
 a vehicle resembling a bicycle but having skis instead of wheels; 
 the rider wears short skis for balancing; 
WordNet (r) 3.0 (2006):
skibob
    n 1: a vehicle resembling a bicycle but having skis instead of
         wheels; the rider wears short skis for balancing