invertebrate

In biological terms, this word describes a vast array of animals ranging from microscopic worms to giant squids. It serves as a broad taxonomic classification rather than a specific species, emphasizing the absence of a vertebral column as the defining physical trait.

When used to describe a person, the term is a sharp metaphor for cowardice or passivity. It suggests a total lack of moral fiber or the inability to maintain a firm position, effectively equating a lack of physical bone structure with a lack of psychological strength.