(usually in the plural) underpants worn by men

Undergarment which is loose fitting.

Loose fitting under shorts.

Usually worn as underwear by men although women also wear boxer shorts as underwear. Usually loose fitting although they can aslo be tight fitting, made of stretchy material. See JK Lingerie mens underwear

Underwear or sleepwear designed with an elastic waistband and open, loose fitting legs. Men wear boxers as undergarments, and women typically as lounge or sleepwear.