Merriam-Webster Collegiate Dictionary - tonsure

 I. noun  Etymology: Middle English, from Anglo-French, from Medieval Latin tonsura, from Latin, act of shearing, from tonsus, past participle of tondere to shear — more at tome  Date: 14th century  1. the Roman Catholic or Eastern rite of admission to the clerical state by the clipping or shaving of a portion of the head  2. the shaven crown or patch worn by monks and other clerics  3. a bald spot resembling a ~  II. transitive verb  (~d; tonsuring)  Date: 1706 to shave the head of; especially to confer the ~ upon