boff

• Verb (vulgar slang): To have sexual intercourse with, or to engage in sexual intercourse. Apparently derives from the word buff in Middle English, which means 'to hit' and itself derives from buffe, an Old French word meaning a blow.
• A slang word for a great success, related to boffo and boffola
• An English schoolboy slang word for a swot or egghead, probably derived from boffin
• British slang word for buttocks
• American slang for a good joke or a good laugh ("Dude, what a boff!") - apparently mainly used in vaudeville
• 1970's Lancashire school slang for a fart
• British slang word for certain kinds of cheap sweets, e.g. apple drops, cola bottles. Apparently the seller of the sweets would be referred to as the Boffy

All of these definitions are from sources on the web, listed below. If anyone can confirm or contradict any of these, e.g. "I grew up in Lancashire in the 1970's and I never heard anyone say that word!", please /msg me.