Definition of unfounded adjective from the Oxford Advanced Learner's Dictionary not based on reason or fact Speculation about a divorce proved totally unfounded. These claims were not altogether unfounded. I was pleased to discover that my fears were unfounded.

Unfounded refers to a claim, accusation, belief, or idea that lacks a solid basis or justification, typically because it is not supported by evidence, facts, logical reasoning or foundations. It is considered groundless, baseless or unsubstantiated.