suppositious

American  

[suhp-uh-zish-uhs] / ˌsʌp əˈzɪʃ əs /

adjective

1. formed from or growing out of supposition.

   suppositious evidence.

2. supposititious.

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suppositious British  

/ ˌsʌpəˈzɪʃəs /

adjective

1. deduced from supposition; hypothetical

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Other Word Forms

• suppositiously
  adverb
• suppositiousness
  noun

Etymology

Origin of suppositious

First recorded in 1615–25; shortened form of supposititious

Explanation

Something you assume to be true without having any real proof is suppositious. If there's no evidence that your brother stole your favorite sweatshirt, it's suppositious to accuse him of the deed. When you use supposition, or an unproven belief, to decide something, that's suppositious. Both words come from suppose and its root, which means "to assume." This adjective is uncommon today — you're more likely to say "unfounded" or "based on an assumption." Still, feel free to pull out suppositious for situations such as the suppositious evidence a substitute teacher uses to punish the whole class for passing notes.

Example Sentences

In a year when snooker's maximum break, once considered as suppositious as the Himalayan Yeti, has repeatedly shown up for the cameras, it fell to O'Sullivan to show that nobody does it better.

From BBC • Dec. 2, 2025

By quotations from suppositious, always unnamed "authorities," by innuendoes and by skilled selection of facts he presumed to prove hat Henry Ford is decaying as a maker of motor cars.

From Time Magazine Archive

The Darien Scheme at best was but suppositious, for no experiment had been tried in order to forecast a realization of what was expected.

From An Historical Account of the Settlements of Scotch Highlanders in America by MacLean, J. P. (John Patterson)

The example may be either actual or suppositious, but it must illustrate clearly and accurately.

From Public Speaking by Stratton, Clarence

You will understand," he added, "that the matter is entirely suppositious.

From Sons and Fathers by Edwards, Harry Stillwell