lobster pot

Short definition from Wiktionary

Noun

1. 1
   A trap used to catch lobsters, resembling a crate with a small opening that a lobster can enter but has trouble exiting.
2. 2
   Synonym of lobster-tailed pot (“kind of helmet”).
3. 3
   Used other than figuratively or idiomatically: see lobster, pot: a pot for cooking a lobster in.