<p><strong>Noun</strong></p><ul><li>(especially collectively) jellyfish, (especially referring to two or more kinds or species) jellyfishes.</li><li>any of various marine coelenterates of a soft, gelatinous structure, especially one with an umbellalike body and long, trailing tentacles; medusa.</li><li>Informal: a person without strong resolve or stamina; an indecisive or weak person.</li></ul>