Longman Dictionary of Contemporary English
The Collaborative International Dictionary
chin-up \chin-up\ n. an arm exercise performed by pulling oneself up on a horizontal bar until the chin is level with or above the bar.
Douglas Harper's Etymology Dictionary
Wiktionary
n. (context US English) An exercise done for strengthening the arms and back, in which one lifts one's own weight while hanging from a bar. It can be defined more restrictively on criteria like the arms starting at lock-out, or the chin requiring contact with the bottom of the bar, or touching the neck to the bar.
WordNet
n. an arm exercise performed by pulling yourself up on a horizontal bar until your chin is level with the bar [syn: pull-up]
Wikipedia
The chin-up (also known as a chin or chinup) is a strength training exercise. People frequently do this exercise with the intention of strengthening muscles such as the latissimus dorsi and biceps, which extend the shoulder and flex the elbow, respectively.
It is a form of pull-up in which the range of motion is established in relation to a person's chin.
In the 1970s and 1980s, the term chin-up not only included an overhand/pronated ("palms away") grip, but some authors used it as the default meaning of the term, with an underhand/supinated ("palms toward") grip called a "reverse" grip. Even in the 2010s "chin-up" still includes palms-away lifting. The term "chin-up" is still regularly used refer to pulling using an overhand-grip.
Both pull-ups and chin-ups are two of the best exercises for back and overall upper body conditioning. However, they target the muscles a bit differently. Both exercises will work the latissimus dorsi and biceps, but standard chin-ups—with an underhand grip—place more emphasis on the biceps.
Usage examples of "chin-up".
The summer of 1982, John had also promised to reward the boys monetarily for their chin-ups, if they reached his goal for them by his chosen deadline.
Her twelve hadn't taken a third as long as his forty-two, and when Esau had finished his chin-ups, Fong had ordered him to do fifty pushups for the backflash.
He told the master sergeant how many chin-ups he'd done, and about the fifty pushups, not withholding what they'd been for.
Then, driven by barking second-tier cadre, they ran hard to the chin-up bars, a bar per man, where they alternated between sets of ten chin-ups, fifteen pushups, and thirty side-straddle hops, each exercise serving as rest from the one before.
Sixty feet away, the trainees were doing their pre-supper chin-ups before going in, callused fists gripping wet bars without a sign of slippage.
As a boy in New Jersey, he made himself strong from chin-ups, push-ups and maniacal repetitions with free weights he constructed from cinder blocks and mop or broom handles.
The men started out drooling, kicked over into laughing and finally wound up competing with each other to show her the proper way to perform squat lifts, chin-ups and leg curls.
A thin man of slightly above average height, he reached up the side of the shuttle to run his hands along the slot in question, pull himself up chin-up fashion, peer about and mutter notes into his recorder.