invertebrate

Lacking a backbone or spinal column; not vertebrate.

Of or relating to invertebrates.

An animal, such as an insect or mollusk, that lacks a backbone or spinal column.

Not vertebrate; having no backbone; specifically, of or pertaining to the Invertebrata. Also invertebral, invertebrated.

Figuratively, flaccid, as if from lack of a backbone; wanting strength, firmness, or consistency; weak; nerveless.