complete defeat; total loss
Used when someone loses overwhelmingly, with no chance of winning. Often implies a one-sided contest or argument.
Yesterday's game was a complete defeat.
議論で彼に丸負けした。
I was totally defeated by him in the argument.
Compound of 丸 (まる, 'whole, complete') and 負け (まけ, 'defeat'). The prefix 丸 intensifies the noun, giving the sense of a total, unmitigated loss.