expression, noun
wearing only underpants; in just one's underwear
Describes a state of undress where someone is wearing only underpants, often used humorously or to emphasize minimal clothing.
彼はパンツ一丁で部屋をうろうろしていた。
He was wandering around the room in just his underpants.
パンツ一丁の姿で玄関に出てしまった
I accidentally went to the front door wearing only my underpants.