trunks (swimming, boxing, etc.)
Refers to sports trunks, especially for swimming or boxing. Not used for casual shorts.
He bought new swimming trunks.
In a boxing match, the fighters wear trunks.
boxer shorts; boxers; trunks (underwear)
Refers to men's underwear, specifically loose-fitting boxer shorts. In Japanese, トランクス is the common term for boxers, while ブリーフ is used for briefs.
He sleeps in boxer shorts.
These boxers are 100% cotton and feel nice against the skin.
He always wears black boxer shorts.
It was so hot that I stripped down to just my boxers.