1. reduction in size: a shrinking or reducing alternate expansion and contraction
2. contracting of body part: a tightening or narrowing of a muscle, organ, or other body part
3. tightening of womb muscles effecting childbirth: a tightening of the muscles of the womb that occurs at increasingly frequent intervals immediately before childbirth and eventually pushes the baby out of the womb
4. shortened word: a shortened form or shortening of a word or phrase, e.g. "he'll" for "he will." In English, the omitted letter or letters are usually marked with an apostrophe or a period, depending on the type of contraction.