What is "supposably"

Supposable \Sup*pos"a*ble\, a. Capable of being supposed, or imagined to exist; as, that is not a supposable case. -- Sup*pos"a*ble*ness, n. -- Sup*pos"a*bly, adv.

"as may be supposed," 1795, not originally American English, alteration of supposedly, or else from supposable (1680s), from suppose (v.) + -able.

adv. 1 able to be supposed or conjectured. 2 (context nonstandard English) supposedly.