Definitions

1. adjective

lacking in decency or propriety of behavior, or not having a cultured or refined manner

“Her undecorous behavior at the formal dinner embarrassed her parents.”

2. noun

a lack of decency or propriety in behavior

“The undecorousness of his comments made it difficult for others to speak to him.”

3. adverb

in an undecorous manner

“She spoke undecorously about the situation, causing a scene.”