Shelley's thought never had any backbone.
Shairp.
To the backbone, through and through; thoroughly; entirely. "Staunch to the backbone." Lord Lytton.
Back"boned" (&?;), a. Vertebrate.
Back"cast` (-kst`), n. [Back, adv. + cast.] Anything which brings misfortune upon one, or causes failure in an effort or enterprise; a reverse. [Scot.]
Back" door" (&?;). A door in the back part of a building; hence, an indirect way. Atterbury.
Back"door", a. Acting from behind and in concealment; backstairs; as, backdoor intrigues.