Wiktionary
backboneless
a. 1 Without a backbone; invertebrate. 2 cowardly, spineless.
Usage examples of "backboneless".
Something backboneless and underhand of that kind would not have surprised him in the least.
The upper part of the body, limp, backboneless, and awry, half propped up against the wall, half falling back upon the outstretched arms, told quite plainly its weird tale of death.
It had the flattish star shape of all the tailless, backboneless creatures of this world, yet with legs, arms, and head that parodied humankind.