In motorcycle chassis
design, a stressed member generally refers to the main stress-bearing components of the frame. This term is used most often when referring to one of the more novel ideas of chassis design, which is the concept that the engine
itself can be a stressed member.
The engine is a big hunk of metal -- more than strong enough to act as a large part of the load-bearing system of a motorcycle. A bike that makes notable use of this idea is the Britten V1000, where everything on the motorcycle essentially bolts directly to mounting points cast into the engine.
Yeah, I see those softlinks. Sure didn't see that joke coming. Sheesh.