What Is a Group of Jellyfish Called? – Jellyfish Collective Nouns.

A collective noun for Jellyfish is a “smack”. Other collective nouns for Jellyfish include a bloom, a fluther, a brood, a smuth, a stuck, and a swarm. The term “smack” is derived from the Middle English word “smakke”, which means a “swift blow”. This term was used to describe the sudden movement of a group of Jellyfish, which is similar to the way a smack is delivered.