D defs.my
Entry 2 senses Webster, 1913

Supposition

/sŭpˌ-əz-ĭsh'-ən/ · Sup·po·si·tion · IPA /ˌsʌpəˈzɪʃən/
01 n. The act of supposing, laying down, imagining, or considering as true or existing, what is known not to be true, or what is not proved.
  1. 1.
    The act of supposing, laying down, imagining, or considering as true or existing, what is known not to be true, or what is not proved.
  2. 2.
    That which is supposed; hypothesis; conjecture; surmise; opinion or belief without sufficient evidence.
    “This is only an infallibility upon supposition that if a thing be true, it is imposible to be false.” Tillotson.
    “He means are in supposition.” Shak.