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completely; absolutely; totally; (not) at all
この問題は丸っ切り理解できなかった。
I couldn't understand this problem at all.
丸っ切り違う方向に進んでしまった。
We ended up going in a completely different direction.
丸っ切り予想が外れて計画を一から練り直す羽目になる。
The prediction was completely wrong, and we ended up having to redo the plan from scratch.