Synonyms of baseless

2 Syllables
groundless, flimsy
3 Syllables
ill-founded, invalid, bottomless, unfounded, ungrounded, gratuitous, reasonless
4 Syllables
unjustified, unwarranted, unprovoked, untenable, nonexistent, unconfirmed, foundationless, unsupported
5 Syllables
unjustifiable, unsubstantiated
6 Syllables
uncorroborated