Wordnet 3.0
NOUN (1)
1. 
 a naked swim; 
VERB (1)
1. 
 bathe in the nude; 
- Example: "The young people were skinny-dipping in the pond"
WordNet (r) 3.0 (2006):
skinny-dip
    n 1: a naked swim
    v 1: bathe in the nude; "The young people were skinny-dipping in
         the pond"