bad form

Webster's Dictionary (1913)

the general appearance, condition or action, originally of horses, afterwards of persons; as, the members of a boat crew are said to be in good form when they pull together uniformly. The phrases are further used colloquially in description of conduct or manners in society; as, it is not good form to smoke in the presence of a lady.

From the entry Form.

Webster’s Revised Unabridged Dictionary (1913), from GCIDE 0.54