Нет. Подштанники это и есть трусы! Только длинные. Ну вот вы про кальсоны слышали?
But too late; Snape had directed his wand straight at James; there was a flash of light and a gash appeared on the side of James’s face, spattering his robes with blood. James whirled about; a second flash of light later, Snape was hanging upside down in the air, his robes falling over his head to reveal skinny, pallid legs and a pair of graying underpants.

И передайте переводчикам Росмена мои матерные слова, underpants British English, underpants refers to only men's underwear - мужские трусы.