in·ver·te·brate 
(ĭn-vûrtə-brĭt, -brāt′)
(ĭn-vûrtə-brĭt, -brāt′)adj.
1. Lacking a backbone or spinal column; not vertebrate.
2. Of or relating to invertebrates: invertebrate zoology.
n.
An animal, such as an insect or mollusk, that lacks a backbone or spinal column.