What is Crab ?
Crab is (noun) 1. an edible sea animal with eight legs, which walks sideways The children caught several little crabs in the rock pools. 2. the meat of this animal, used as food He ordered a crab sandwich. 3. to catch a crab to miss a stroke when rowing One of the rowers caught a crab and all the others stopped rowing.
source: Easier English, Student Dictionary Upper Intermediate Level