The suppression of a vowel or syllable for metrical purposes. E.g. 'The sedge has wither'd from the lake' from La Belle Dame Sans Merci by Keats. The elision, in this case, ensures that the line remains octosyllabic. Modern poets no longer use elision. See also synalepha.
[n] a deliberate act of omission; "with the exception of the children, everyone was told the news"
[n] omission of a sound between two words (usually a vowel and the end of one word or the beginning of the next)