Fanny
Seat
arse
ass
backside
behind
bottom
bum
buns
butt
buttocks
can
croup
croupe
derriere
fundament
hind end
keister
posterior
prat
rear
rear end
rump
stern
tail
tail end
tooshie
tush
body part
buttock
dress-suit
haunch
hooves
riding-coat
sirloin
thornbush