Noun
1. decapod having eyes on short stalks and a broad flattened carapace with a small abdomen folded under the thorax and pincers
2. a quarrelsome grouch
3. the edible flesh of any of various crabs
4. infests the pubic region of the human body
5. a stroke of the oar that either misses the water or digs too deeply;
"he caught a crab and lost the race"