infestation of the pubic hair by crab lice
"After visiting that crowded beach, he realized he had picked up crabs and was itching all over his groin area."
plural of crab
"The doctor warned him that swimming in dirty water could expose him to crabs, a sexually transmitted infestation that causes intense itching."
pubic lice
Third-person singular simple present indicative form of crab
"The crabs at the beach party are dancing to the music."