Of opinions, propositions, doctrines, representations: Contrary to what is true, erroneous.

Not based or established in something.

(un-, prefix1 affix 1b affix 5.)

Of doctrines, opinions, statements, etc.: Containing errors; of the nature of error; incorrect, mistaken, wrong.

Of belief, etc.: Partaking of or based on error; erroneous.

Not based on sound or reliable evidence or reasoning; unsound, fallacious.

Wrongly conceived, entertained, or carried out; erroneous.

Of an opinion, belief, etc.: not in accordance with established doctrine; unsound, heretical. Obsolete.

Esp. of an opinion: erroneous, unsound; not in accordance with established doctrine; = sinister, adj. 5a. Obsolete.

Erroneous, faulty.

figurative. Having no substance or sound basis.

Not soundly based in reasoning or fact.

Falsely grounded, unjustified; ill-founded.

Of an opinion, statement, etc.: mistaken, erroneous. Obsolete.

= erroneous, adj.

Having no proper foundation; unsupported; not founded on or in something.

Erroneous, mistaken.

Of doctrines, opinions, etc.: Not in accordance with established doctrines or opinions, or those… generally.

(un-, prefix1 affix 2.)

Felt incorrectly or imperfectly.

Of thought, etc.: imprecisely defined; confused, vague. Also of persons: inexact in thought or expression.

slang (originally U.S.). Of an object, idea, etc.: characteristically eccentric or crazy; outrageous, unusual; also, unreliable or erratic.