noun, noun or participle which takes 'suru', intransitive verb
tonsure; shaving one's head (upon entering the Buddhist priesthood)
Specifically refers to the ritual shaving of the head when becoming a Buddhist monk or nun. Can also be used as a noun or a suru-verb.
彼は出家するために剃髪した。
He shaved his head to enter the priesthood.
剃る is the general verb for shaving hair from the body, while 剃髪 is specifically the ritual head-shaving for Buddhist ordination.
From 剃 (shave) + 髪 (hair). The term is closely associated with Buddhist ordination rites.