entirely; (not) at all
犯人は皆目見当がつかない。
I have no idea at all who the culprit might be.
彼の意図は皆目わからず、途方に暮れた。
His intentions were entirely beyond me, and I was at a loss.
昔の出来事は皆目思い出せず、記憶が全く消えていた。
I could not recall the old events at all; the memory had vanished entirely.