Definition of pull-ups:
(n) :
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.
(v) :
To do a pull-up or pull oneself up similarly.
(n) :
Synonym of training pants (“undergarments worn by incontinent people, typically infants, to aid in toilet training during the transition between diapers and underpants”).
(n) :
(electronics) A pull-up resistor.