noun
behavior that is not in keeping with accepted standards of what is right or proper
adjective
indecorous (not in keeping with accepted standards of what is right or proper)
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The ambassador's behavior at the state dinner was considered indecorum by the other guests.
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She was shocked by the indecorum of his loud outburst during the meeting.
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I can't believe the indecorum of that guy at the party last night.
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The painting's use of bright colors may be seen as indecorum in traditional art circles.