Rude, ill-mannered, impolite, discourteous, uncivil, ungracious can all mean not observant of the manner or forms required by good breeding.
Rude suggests lack of delicacy or consideration for the feelings of others; it does not necessarily suggest lack of breeding, for it is applicable to persons of all stations or conditions. It usually stresses impudence, insolence, or a generally insulting manner.
Ill-mannered is a more general and less explicit term, and it seldom carries a suggestion of an intent to offend or insult such as rude usually carries; it is therefore applicable to a person, act, or utterance that shows ignorance of, indifference to, or a disregard of the proprieties.
Impolite, discourteous, and uncivil, as the negatives of polite, courteous, civil ((for all three, see CIVIL )) imply merely the reverse of the care in observing the proprieties of good or formal society that is suggested by polite or of the considerate, dignified politeness that is suggested by courteous, thereby implying something like rudeness or of the modicum of good manners that is suggested by civil, thereby implying an utter disregard of the decent consideration expected in social intercourse among civilized persons.
Ungracious (compare GRACIOUS ) stresses the lack of kindliness or courtesy resulting from awkwardness, callowness, surliness, or irritation.