* Baseless: Without any supporting evidence or justification.
* Unfounded: Not supported by any real or logical reasons.
* Frivolous: Trivial, insignificant, and without merit.
* Without merit: Lacking any valid claim or argument.
Examples:
* "The accusations against her were completely groundless. There was no proof to support them."
* "His fears about the future were groundless and only served to make him anxious."
* "The lawsuit was dismissed because it was based on a groundless claim."
Essentially, something that is groundless is without any real substance or validity.