noun. One or more unstressed syllables at the beginning of a line of verse, before the reckoning of the normal meter begins.

noun. undefined

noun. In prosody, an upward beat at the beginning of a verse, consisting of either one or two unaccented syllables, regarded as separate from and introductory to the remainder of the verse.

noun. A prefix of one or two unaccented syllables to a verse properly beginning with an accented syllable.

noun. An unstressed syllable at the start of a verse.

noun. An unstressed note or notes before the first strong beat (or downbeat) of a phrase.

"3. The first word of “The Star-Spangled Banner” “Oh” is an example of the literary device known as anacrusis, a lead-in syllable or syllables that precede the first full foot."