Real Dictionary

push-up
countable noun: Push-ups are exercises to strengthen your arms and chest muscles. They are done by lying with your face towards the floor and pushing with your hands to raise your body until your arms are straight.

push-up in American English
an exercise in which a person lying face down, with the hands under the shoulders, raises the body by pushing down with the palms: push-ups are usually done in series by alternately straightening and bending the arms
adjective: having padding and usually underwires in the lower part of the cups so as to raise the breasts and make them seem fuller
noun: an exercise in which a person, keeping a prone position with the hands palms down under the shoulders, the balls of the feet on the ground, and the back straight, pushes the body up and lets it down by an alternate straightening and bending of the arms

push-up in British English
noun: an exercise in which the body is alternately raised from and lowered to the floor by the arms only, the trunk being kept straight with the toes and hands resting on the floor