The word impudent refers to a person who lacks respect for others. The person may be marked by contemptuous behaviour or disregard of others. Some common synonyms of impudent are impertinent, insolent, cheeky, audacious, brazen, disrespectful, etc. A common antonym of the word, impudent, is respectful.
Example – He is the most impudent fellow I know, so I do not want to go out to dinner with him.