lazy ass; slow to act; reluctant to get moving
Idiomatic expression literally meaning 'heavy buttocks'. Used to describe someone who is sluggish, unwilling to get up, or slow to take action. Often used in a teasing or mildly critical way. Compare with 腰が重い, which focuses more on reluctance to start a task.
See also: 尻が重い
He's a lazy ass and won't get moving easily.
Even after the meeting ends, many people are slow to get up.
Compound of 重い (heavy) and 尻 (buttocks). The figurative meaning of laziness or sluggishness comes from the image of a heavy bottom that is hard to lift.