good/bad form

bad form

Behavior or actions that are considered socially inappropriate, distasteful, or rude. Many people still consider it bad form to ask a woman her age.
See also: bad, form
Farlex Dictionary of Idioms.

good/bad ˈform

(old-fashioned, British English) a way of doing things that is socially acceptable/not socially acceptable: I think it was very bad form for Joe to arrive late for the funeral. Apparently, good form requires you to wear a hat on these occasions.
See also: bad, form, good
Farlex Partner Idioms Dictionary
See also:
  • bad form
  • poor form
  • in bad form
  • look bad
  • suck face
  • rum
  • DOS
  • a rum do
  • a rum go