leg curl

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An exercise, usually performed lying on the stomach with weights, in which one lifts one or both heels towards the buttocks and then returns to the starting position, while the rest of the body is kept immobile.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun weightlifting An exercise performed on a machine in which the hamstring muscles are exerted to bend the knee while acting against resistance applied to the lower calf. The exercise may be performed while prone or standing, depending on the design of the machine.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an exercise designed to strengthen the flexor muscles of the leg