Green’s Dictionary of Slang

usu. of people, a (very great) bore.

1843		R.S. Surtees Handley Cross (1854) 159: A couple of regular cut-’em-down swells, viz., Captain Arthur Crasher [...] and Captain Blucher Brusher.
1858		R.S. Surtees Ask Mamma 184: All of which Billy received with the most provoking indifference, making the Major wish he mightn’t be a regular crasher, who cared for nothing but riding.
2012		Guardian 29 Apr. 🌐 Like many autocrats, he’s a bit of a crasher, astonishingly incurious and profoundly lowering.