Dictionary / Vocabulary / 禁物
きんもつ
thing that should be (carefully) avoided; no-no; thing to definitely not do; something forbidden
JLPT N1 common word
彼女に太ったねなんて言うのは禁物だ。
Don't mention that she's put on weight.
長くつき合うには掛けは禁物。
Short accounts make long friends.
長い付き合いにかけは禁物。