1) Arcane 2) Beyond belief 3) Confusing 4) Cryptic 5) Cryptical 6) Enigmatic 7) Enigmatical 8) Esoteric 9) Illegible 10) Inarticulate 11) Indecipherable 12) Inexplicable 13) Inscrutable 14) Missed 15) Mumbled 16) Mysterious 17) Mystifying 18) Paradoxical 19) Puzzling 20) Unaccountable 21) Uncomprehensible 
• (a.) Not capable of being contained within limits. • (a.) Not capable of being comprehended or understood; beyond the reach of the human intellect; inconceivable.
In·com`pre·hen'si·ble adjective [ Latin incomprehensibilis : confer French incompréhensible . See In- not, and Comprehensible .] 1. Not capable of being contained within limits. « An infinite and incomprehensible substance.» Hooker. ...
[adj] - difficult to understand
uncomprehensible adjective difficult to understand; `the most incomprehensible thing about the universe is that it is comprehensible`- A. Einstein
impossible to understand or comprehend; unintelligible. · limitless; not limited or capable of being limited.