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Meaning of sit-up

sit-up

Pronunciation: (sit'up"), [key]
— n.
  1. an exercise in which a person lies flat on the back, lifts the torso to a sitting position, and then lies flat again without changing the position of the legs: formerly done with the legs straight but now usually done with the knees bent.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.