Wordnet 3.0
NOUN (1)
1. 
 a definition in which the term is used by embedding it in a larger expression containing its explanation; 
- Example: "a contextual definition of `legal duty' might be `X has a legal duty to do Y means that X is required to do Y by a contract relationship that would be upheld in a court of law'"
WordNet (r) 3.0 (2006):
contextual definition
    n 1: a definition in which the term is used by embedding it in a
         larger expression containing its explanation; "a contextual
         definition of `legal duty' might be `X has a legal duty to
         do Y means that X is required to do Y by a contract
         relationship that would be upheld in a court of law'"