noun
long men's underpants; loose Bermuda-style underpants
A type of men's underwear resembling loose, knee-length shorts, often worn under trousers. Considered old-fashioned by younger generations but still used for comfort or as loungewear.
夏はステテコで過ごすのが涼しくて好きだ。
In summer, I like spending time in step-in underpants because it's cool.
祖父はいつもステテコをはいている。
My grandfather always wears long underpants.
The origin is uncertain. One theory suggests it comes from the sound of walking in loose clothing, but this is not confirmed.