What is the meaning of Pull-up?

An exercise done for strengthening the arms and back in which one lifts one's own weight while hanging from a bar. Palms may be facing in any direction.

To do a pull-up or pull oneself up similarly.

Synonym of training pants (undergarments worn by incontinent people, typically infants, to aid in toilet training during the transition between diapers and underpants).

A pull-up resistor.

Source: wiktionary.org