1. Rigid, turgid, barely flexible.
2. A corpse (dead long enough to have rigor mortis).
3. Cheat ("I got stiffed")
4. Ordinary man. ("You lucky stiff.")
5. Stand-up (a stiff collar... etc).
6. Loaded to the gills,pissed
7. Very. ("bored stiff")

See also: stiffy,stiffie