bottom

[1]	penetrate , fathom

[1]	underside , seat , buttocks , undersurface , rear , behind , rear end , derriSre , rump , posterior , hindquarters , breech , fundament , gluteus maximus , (Colloq) backside , butt , prat , (Brit) bum , (US) can , duff , keister/keester , hinie , (Colloq) (Brit) arse , (US) ass , (Slang) (US) tokus/tochis/tuchis , tushie/tushy/tush
[2]	base , foot , foundation , groundwork , substructure , footing , underpinning , fundament
[3]	basis , buttocks , nates , foundation , source , arse , butt , origin , cause , backside , bum , heart , nub , buns , can , fundament , hindquarters , hind end , keister , posterior , prat , rear , rear end , rump , stern , seat , tail , tail end , tooshie , tush , behind , derriere , fanny , ass
[4]	bottom of the inning , depths , Davy Jones's locker , bed
[5]	at bottom , bed , basically , fundamentally , in the final/last analysis , really , in reality , truly , in truth , essentially
[6]	Bottoms up , bottomland , Prosit , To your (very good) health , Cheers , Here's to , Skol
[7]	freighter , merchantman , merchant ship