Wordnet 3.0
NOUN (1)
1. 
 a biter who takes dainty repeated bites; 
The Collaborative International Dictionary of English v.0.48:
Nibbler \Nib"bler\, n.
   One who, or that which, nibbles.
   [1913 Webster]
WordNet (r) 3.0 (2006):
nibbler
    n 1: a biter who takes dainty repeated bites