1) Musical upbeat 2) Upbeat 
In poetry, a set of extrametrical syllables at the beginning of a verse is said to stand in anacrusis (ἀνάκρουσις `pushing up`). The technique is seen Old English poetry; in lines of iambic pentameter, the technique applies a variation on the typical pentameter line causing it to appear at first glance as trochaic. In music, an anacru.....[genus] Anacrusis is a genus of moths belonging to the subfamily Tortricinae of the family Tortricidae. ...
a note or notes that precede the first full bar; a pickup
syllable prior to the normal rhythm of a verse
• (n.) A prefix of one or two unaccented syllables to a verse properly beginning with an accented syllable.
in classical prosody, the up (or weak) beat, one or more syllables at the beginning of a line of poetry that are not regarded as a part of the ...
a note or notes that precede the first full bar; a pickup
The addition of an extra unstressed syllable or two at the start of a line of verse--but these addit
An`a·cru'sis noun [ Greek ..., from ... to push up or back; ... + ... to strike.] (Pros.) A prefix of one or two unaccented syllables to a verse properly beginning with an accented syllable. 
Unstressed syllable(s) occurring at the start of a line which do not contribute to the meter.
a note or notes that precede the first full bar; a pickup
an unstressed syllable or syllable group that begins a line of verse but is not counted as part of the first foot. · the note or notes preceding a downbeat; upbeat.