'Invertebrate' definitions:

Definition of 'invertebrate'

From: WordNet
adjective
Lacking a backbone or spinal column; "worms are an example of invertebrate animals" [syn: invertebrate, spineless] [ant: vertebrate]
noun
Any animal lacking a backbone or notochord; the term is not used as a scientific classification

Definition of 'Invertebrate'

From: GCIDE
  • Invertebrate \In*ver"te*brate\, a. (Zool.) Destitute of a backbone; having no vertebr[ae]; of or pertaining to the Invertebrata. -- n. One of the Invertebrata. [1913 Webster]
  • Age of invertebrates. See Age, and Silurian. [1913 Webster]