baseless, bottomless, built on sand, chimerical, empty, flimsy, gratuitous, hypothetical, idle, ill-founded, illusory, imaginary, inconclusive, indecisive, not following, not proved, not well-founded, speculative, suppositional, tenuous, unascertained, unattested, unauthenticated, unbased, uncalled-for, uncertified, unconfirmed, uncorroborated, undemonstrated, undetermined, unestablished, unfixed, unfounded, ungrounded, unjustifiable, unjustified, unproved, unproven, unreasonable, unsettled, unshown, unsound, unsubstantiated, unsupportable, unsupported, unsupported by evidence, unsustainable, unsustained, untenable, untested, untried, unvalidated, unverified, unwarranted, vain, without basis, without foundation, without grounds