1The action of supposing something, supposition. Formerly often in "on (also †upon) supposal of (also †that)". Also parenthetically, "†by (also upon) supposal": as may be supposed, supposedly (obsolete).
2Something supposed; a supposition, a hypothesis, a conjecture; an assumption.
"†by supposals": as may be supposed, supposedly (obsolete).
3 rare A notion, an opinion.
Late Middle English; earliest use found in John Wyclif (d. 1384), theologian, philosopher, and religious reformer. From Anglo-Norman supposaille, supposail, supposaile mere supposition, (in law) a supposition, something presupposed to be true from supposer + -aille, -ail.