Same word as vague:

ambiguous, amorphous, amphibological, bewildering, bleary, blurred, cloudy, dark, dim, doubtful, dreamlike, dubious, enigmatic, equivocal, faint, fuzzy, generalized, hazy, ill-defined, impalpable, imprecise, indefinite, indeterminate, indistinct, inexplicable, lax, loose, misunderstood, muddy, nebulous, obscure, perplexing, problematic, puzzling, questionable, shadowy, superficial, tenebrous, uncertain, unclear, undetermined, unexplicit, unintelligible, unknown, unsettled, unspecified, unsure