n. The loss of the initial unstressed vowel of a word.
the GNU version of the Collaborative International Dictionary of English
n. The loss of a short unaccented vowel at the beginning of a word; -- the result of a phonetic process.
The Century Dictionary and Cyclopedia
n. The gradual and unintentional removal of a short unaccented vowel at the beginning of a word; a special form of apheresis, as in squire for esquire, down for adown, etc.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. the gradual disappearance of an initial (usually unstressed) vowel or syllable as in `squire' for `esquire'
Word Usage
"Among phonetic changes which occur with more or less regularity are those called aphesis, epenthesis, epithesis, assimilation, dissimilation, and metathesis, convenient terms which are less learned than they appear."