Definition of "jellyfish" []

• Any of numerous usually free-swimming marine coelenterates of the class Scyphozoa, characteristically having a gelatinous, tentacled, often bell-shaped medusoid stage as the dominant phase of its life cycle. (noun)
• Any of various similar or related coelenterates. (noun)
• Informal One who lacks force of character; a weakling. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The term "jellyfish" often is used to denote weakness."
• "The term "jellyfish" encompasses two different groups: Cnidaria, animals"
• "From the edge, which emit green light when the jellyfish is agitated, Shimomura isolated a protein."