A pin-up girl, also known as a pin-up model, is a model whose mass-produced pictures see wide appeal as popular culture. Pin-ups are intended for informal display, e.g. meant to be "pinned-up" on a wall. Pin-up girls may be glamour models, fashion models, or actresses.
The term pin-up may also refer to drawings, paintings, and other illustrations done in emulation of these photos. The term was first attested to in English in 1941 however, the practice is documented back at least to the 1890s.
The pin-up images could be cut out of magazines or newspapers, or be from postcard or chromo-lithographs, and so on. Such photos often appear on calendars, which are meant to be pinned up anyway. Later, posters of pin-up girls were mass-produced and became an instant hit.