非常識|ひじょうしきhijoushiki[2]nakadaka (mid-high)

1. noun, na-adjectivelack of common sense; thoughtlessness; senselessness; irrationality; absurdity
   あんなことを彼女かのじょに言ゆうなんて非常識ひじょうしきも甚はなはだしい。↗

   It's quite absurd of you to tell her that sort of thing.

• Related不合理ふごうりWrittenWritten/formal prose. Points to what is illogical, as in 「不合理な制度」; 「非常識」 is about breaching social common sense and the rules.
• Related筋違いすじちがいNeutralNeutral. Aiming at the wrong target or contrary to reason, as in 「筋違いな文句」; 「非常識」 is about not knowing the rules.
• Related無茶むちゃNeutralNeutral. Wild or reckless behaviour, as in 「無茶な要求」; stresses rashness and need not flout common sense.
• Related理不尽りふじんNeutralNeutral. High-handed unreasonableness, as in 「理不尽な要求」; carries the resentment of the one on the receiving end.
• Related荒唐無稽こうとうむけいWrittenWritten/formal prose. A four-character idiom for what is preposterous and utterly groundless; said mostly of stories, claims and plans, but also of words and deeds.
• Related馬鹿らしいばからしいCasualColloquial. Foolish and laughable, as in 「馬鹿らしくてやってられない」.
• RelatedとんちんかんCasualColloquial. Remarks wildly off the point or answers that miss the question; stresses a mismatch in understanding.
• RelatedばかばかしいCasualColloquial. So absurd it is laughable and not worth the bother; stresses the comical side, where 「非常識」 stresses the discourtesy.
• Related阿呆らしいあほらしいNeutralKansai colloquial. Absurd and pointless, said with disdain; close to 「馬鹿馬鹿しい」.
• Related馬鹿げたばかげたNeutralNeutral. Absurd and foolish; used prenominally, as in 「馬鹿げた話」; said chiefly of ideas.
• RelatedバカくさいCasualColloquial. Pointless and laughable, said with disdain, as in 「バカ臭くてやめた」.
• RelatedアホくさいNeutralKansai colloquial. So absurd it saps your will to bother, said with disdain.
• Antonym常識じょうしきNeutralCommon sense and social rules, as in 「常識がない」; the direct opposite of 「非常識」.
• Antonym分別ふんべつNeutralThe judgement to tell right from wrong, as in 「分別のある大人」; the opposite of 「非常識」.

Use 「非常識」 for ignoring the rules and social common sense, as in 「非常識な時間に電話する」. For the illogical pick 「不合理」, for high-handed unreasonableness 「理不尽」, and for the opposite quality 「常識」. The rest mostly stress recklessness (「無茶」), being off the point (「頓珍漢」) or absurdity (「馬鹿げた」).

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 常識じょうしきはずれなこと。常識じょうしきがないこと。