Wordnet 3.0
NOUN (1)
1. 
 a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; 
 constitutes 21 percent of the atmosphere by volume; 
 the most abundant element in the earth's crust; 
[syn: oxygen, O, atomic number 8]
WordNet (r) 3.0 (2006):
atomic number 8
    n 1: a nonmetallic bivalent element that is normally a colorless
         odorless tasteless nonflammable diatomic gas; constitutes
         21 percent of the atmosphere by volume; the most abundant
         element in the earth's crust [syn: oxygen, O, atomic
         number 8]