noun, na-adjective
extreme foolishness; grave stupidity
Describes a state or act of great stupidity; often used as a noun or adjectival noun (e.g., 大馬鹿なことをする).
そんな大馬鹿な話は聞いたことがない。
I've never heard such an utterly foolish story.
彼は大馬鹿な失敗をしてしまった。
He made a terribly stupid mistake.
noun
big fool; utter idiot
Refers to a person who is extremely foolish; carries a strong derogatory tone.
あいつは本当に大馬鹿だ。
That guy is a complete idiot.
大馬鹿め！何をやっているんだ。
You utter fool! What are you doing?
馬鹿 means 'fool' or 'stupidity'; 大馬鹿 intensifies it to 'extreme foolishness' or 'big fool'.
Compound of 大 (おお, 'big') and 馬鹿 (ばか, 'fool'). The origin of 馬鹿 is uncertain, possibly from Sanskrit or a Chinese story, but the exact derivation is unclear.