no-no 
noun (plural no-nos) informal
A thing that is not possible or acceptable: perming highlighted hair used to be a definite no-no, but it’s now possible...
- So an office at that end of the building is a definite no-no as the droning hum could drive me mad.
- That sort of event was a definite no-no and he worked hard to prevent such things.
- Wiggling out was a definite no-no since he had already made sure that I had nowhere else to turn to.
Rhymes
- non-randomness
- non-rational
- non-rationality
- non-reactionary
- non-reactive
- non-reader
- non-reading
- non-realist
- non-realistic
- non-recognition
- non-recoil
- non-recourse
- nonrecurring
- non-reducible
- non-reducing
- non-reduction
- non-referential
- nonrefillable
- non-reflexive
- non-refoulement
- non-refundable
- non-regent
- non-regular
- non-regulation
- non-relational