Synonyms and related words :
baseless, controvertible, empty, groundless, idle, ill-founded, unattestable, unbased, unconfirmable, undemonstrable, undemonstratable, unfounded, ungrounded, unprovable, unsubstantiatable, unsupportable, unsupported, unsustained, untenable, unverifiable, unwarranted, vain, without basis, without foundation