Synonyms of groundless

2 Syllables
flimsy, idle, idlest, empty, false
3 Syllables
causeless, baseless, bottomless, unfounded, ungrounded, gratuitous
4 Syllables
unjustified, illusory, illogical, chimerical, unwarranted, unprovoked, uncalled-for, nonexistent, foundationless, unsupported
5 Syllables
unjustifiable, unauthorized, imaginary
6 Syllables
uncorroborated