Definition of suppositious in English:

suppositious

adjective

  • Based on assumption rather than fact.

    ‘most of the evidence is purely suppositious’
    • ‘No wonder Meg left the biz to focus on something a little less suppositious.’
    unconfirmed, unsupported, uncorroborated, not backed up by evidence, unverified, unattested, unproven, not validated, untested
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Origin

Early 17th century (in the sense supposititious): partly a contraction of supposititious, reinforced by supposition.

Pronunciation:

suppositious

/ˌsəpəˈziSHəs/