Definitions of crayfish:

• noun:   small freshwater decapod crustacean that resembles a lobster
• noun:   tiny lobster-like crustaceans usually boiled briefly
• noun:   warm-water lobsters without claws; those from Australia and South Africa usually marketed as frozen tails; caught also in Florida and California
• noun:   large edible marine crustacean having a spiny carapace but lacking the large pincers of true lobsters