Pronunciation: (dī'u-fōn"), [key]
1. a foghorn producing a low-pitched, penetrating signal of two tones.
a. a phoneme in one dialect corresponding to a similar but phonetically different phoneme in a related dialect.
b. a group of sounds comprising all the phonetically different dialectal variants of a given phoneme in a language: The broad a and flat a of “half ” are members of a single diaphone.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.