Definitions for crab louse
Random House Webster's College Dictionary
a crablike louse, Phthirus pubis, that infests pubic hair and other body hair in humans.
Origin of crab louse:
crab louse, pubic louse, crab, Phthirius pubis(noun)
a louse that infests the pubic region of the human body
A parasitic insect, Phthirus pubis, that lives amongst the pubic hairs of humans and feeds on blood.