Webster’s Revised Unabridged Dictionary · 1913
Bushwhacker
Bush′whack′er (·hwăk′ẽr), n. 1. One accustomed to beat about, or travel through, bushes. [U.S.]
They were gallant bushwhackers, and hunters of raccoons by moonlight. W. Irving.
2. A guerrilla; a marauding assassin; one who pretends to be a peaceful citizen, but secretly harasses a hostile force or its sympathizers. [U.S.] Farrow.