adj. Having no strong foundation; not based on solid reasons or facts.
the GNU version of the Collaborative International Dictionary of English
adj. Not founded; not built or established.
adj. Having no foundation; baseless; vain; idle.
The Century Dictionary and Cyclopedia
Not founded; not built or established. Having no foundation; vain; idle; baseless: as, unfounded expectations.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. without a basis in reason or fact
Word Usage
"Mr. da Silva, who is using his immense popularity to lift his former chief-of-staff Ms. Rousseff into the presidency, appeared on television this week to defend Ms. Rousseff against what he described as unfounded attacks."