impossible to understand or comprehend; unintelligible.

Archaic . limitless; not limited or capable of being limited.

adjective

comprehensible , fathomable , intelligible , understandable

adjective

baffling , beats me , beyond comprehension , beyond one’s grasp , clear as mud , cryptic , delphic , enigmatic , fathomless , greek , impenetrable , incognizable , inconceivable , inscrutable , mysterious , mystifying , obscure , opaque , over one’s head , perplexing , puzzling , sibylline , unclear , unfathomable , ungraspable , unimaginable , unintelligible , unknowable , uncomprehensible , abstruse , ambiguous , confusing , indefinite , nebulous , numinous , undecipherable , unreadable , unthinkable