say it: JEL-ee-fish
jellyfish is a noun meaning "large siphonophore having a bladderlike float and stinging tentacles". It carries 2 recorded senses.
large siphonophore having a bladderlike float and stinging tentacles
any of numerous usually marine and free-swimming coelenterates that constitute the sexually reproductive forms of hydrozoans and scyphozoans
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for jellyfish come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.