na-adjective
awfully; extremely; recklessly
Emphatic adverbial/adjectival use meaning 'excessively' or 'recklessly'. Often interchangeable with むちゃくちゃ, but can carry a slightly softer or more childish tone. Used in casual speech.
See also: 無茶苦茶 (むちゃくちゃ)
今日はむちゃむちゃ暑いね。
It's awfully hot today, isn't it?
彼はむちゃむちゃな運転をする。
He drives recklessly.
Reduplication of むちゃ (無茶), which itself is of uncertain origin, possibly from a Chinese-derived term or a sound-symbolic formation. The exact derivation is unclear.