When someone goes out into nature and violently, immorally, and rudely thrashes around knocking, breaking branches without caring. Sometimes harms cute animals and habitat. If used as an insult should be yelled directly and very enthusiastically. Mainly used by high school biology teachers to insult rude children.
In game, bushwacker is a guy or girl runs around with a knife killing everyone they see while stalking them. It may also be a person in a guinea suit running around killing people and camping .