expression, i-adjective
unthinkable; unimaginable; inconceivable
Expresses that something is beyond what one can imagine or consider possible. Often used in negative potential form 考えもつかない.
See also: 考えつく (かんがえつく)
そんなことは考えもつかなかった。
I never even thought of such a thing.
彼が失敗するなんて考えもつかない。
It's unthinkable that he would fail.
考えつく is the affirmative potential form meaning 'to think of' or 'to come up with an idea'. 考えもつかない is its negative counterpart, emphasizing that something is beyond imagination.
From 考える (to think) + も (even) + つく (to arrive at, to come to mind) in its negative potential form. The expression literally means 'cannot even think of'.