Meaning : The fleshy part of the human body that you sit on.
Example :
He deserves a good kick in the butt.
Are you going to sit on your fanny and do nothing?.
Synonyms : arse, ass, backside, behind, bottom, bum, buns, butt, can, derriere, fanny, fundament, hind end, hindquarters, keister, nates, posterior, prat, rear, rear end, rump, seat, stern, tail, tail end, tooshie, tush