Calzoncillos is a Spanish term that refers to men's underwear, specifically a type of close-fitting, tight-fitting or form-fitting undergarment. In porn videos, this tag might be used to denote scenes where the focus is on male genitals and buttocks encased in tight briefs, boxer briefs, or other revealing underwear styles. The tag implies that viewers are interested in seeing aroused, erect penises, as well as male models showcasing their toned physiques in form-fitting undergarments.