Formal:
* Rude
* Discourteous
* Impolite
* Uncivil
* Boorish
* Unrefined
Informal:
* Crass
* Unmannerly
* Ill-bred
* Ungentlemanly/Unladylike
* Rough around the edges
* A bit of a wild card (suggests the person is not intentionally rude, but lacks social awareness)
More specific:
* Disrespectful (lacking respect for others)
* Inconsiderate (not thinking about the feelings of others)
* Uncultured (lacking knowledge of social customs)
* Insolent (being offensively disrespectful)
The best synonym to use will depend on the specific context and the level of formality you need.