Wordnet 3.0
NOUN (1)
1. 
 an informal term for a father; 
 probably derived from baby talk; 
[syn: dad, dada, daddy, pa, papa, pappa, pop]
WordNet (r) 3.0 (2006):
pappa
    n 1: an informal term for a father; probably derived from baby
         talk [syn: dad, dada, daddy, pa, papa, pappa,
         pop]