Definition - When one or many unstressed syllables start a line of verse before the actual meter begins.

Example -
In the song Star Spangled Banner, the Oh! in Oh! Say can you see is an anacrusis.

Etymology -
The word derives from Greek anakrousis, a pushing back (from ana, back + krouein, to strike).

Oxford English Dictionary -
Its first citation is from 1833:
"The Iambus … in technical language is said to consist of anacrusis and arsis."
(Edin. Rev. LVI. 372 )

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