One who bashes something, figuratively or literally.
One who engages in gratuitous physical or verbal attacks on a group or type of people.
He was beaten up by a queer-basher.
A trainspotter. http//groups.google.co.uk/groups/search?q=%22bashers%22+uk+railway&btnG=Search&sitesearch=groups.google.com
A rainproof sheet for sleeping under.