Wordnet 3.0
NOUN (1)
1.
(linguistics) any of various acoustically different forms of the same phoneme;
The Collaborative International Dictionary of English v.0.48:
allophone \allophone\ n.
any one of two or more speech sounds that considered variants
of the same phoneme. For example, the p sounds of pin and
spin are allophones of p; and the t sounds of toe stop and
catnip are allophones of t.
[PJC]
WordNet (r) 3.0 (2006):
allophone
n 1: (linguistics) any of various acoustically different forms
of the same phoneme