Fetching details from the dictionary...

completely; absolutely; totally; (not) at all
彼の話はまるっきり嘘だったとわかった。
I found out his story was a complete lie.
彼女はまるっきり何も知らなかった。
She didn't know anything at all.
まるっきり予想と違う結果になった。
The result was completely different from expected.