屁股

butt; ass; buttock; bottom; rear; arse; behind; backside; buns; bum; rump; posterior; derriere; fanny; booty; wazoo; jacksie; keister; cheek; duff; tush; seat; back end; rear end

后面

behind; back; rear; reverse; latter; hind; at the back; the back side; in the rear; in the future