Wordnet 3.0
NOUN (1)
1. 
 a gesture of greeting or elation; 
 one person's upraised palm slaps the upraised palm of another person; 
WordNet (r) 3.0 (2006):
high-five
    n 1: a gesture of greeting or elation; one person's upraised
         palm slaps the upraised palm of another person