Spurious (adjective)

1. Not genuine or authentic, but having the appearance of being so.
2. Not being what it purports to be; false or fake.
3. Not having a valid basis, not being supported by facts or evidence.

Origin:

From the latin word "spuriu" which means "bastard" or "illegitimate", it refers to something that is not genuine, authentic or true.

Examples:

1. The painting was found to be spurious, a forgery.
2. The argument was spurious, it was not based on facts.
3. The document was spurious, it was not a real document.
4. The claim was spurious, it was not supported by evidence.
5. The results of the experiment were spurious, they were not reliable.