na-adjective
Used to describe intense criticism or harsh treatment, often with verbs like 言う, 批判する, or けなす. Strongly colloquial and somewhat vulgar.
上司に企画をくそみそに言われた。
My boss harshly criticized my proposal.
ネットでくそみそに叩かれた。
I got severely bashed online.
na-adjective
mixing good and bad; treating all alike
Describes a situation where valuable and worthless things are lumped together without distinction. Often used in the phrase くそみそにする. Less common than sense 1.
彼は名作も駄作もくそみそにして批評した。
He criticized masterpieces and trash alike, treating them the same.
引っ越しのとき、必要なものと不要なものをくそみそ
When moving, I packed necessary and unnecessary things together without sorting.
Compound of 糞 (くそ, 'feces') and 味噌 (みそ, 'miso'). The combination of something foul and something valuable gives rise to the meanings of harsh criticism and mixing good with bad. The exact historical derivation is uncertain.