"Showed out" is a slang term that means to behave in an overly bold or attention-seeking manner, often in a negative way. Antonyms for "showed out" would be words that describe behaviors that are subdued or restrained. Synonyms for these antonyms include words like modest, humble, discreet, restrained, and reserved. Examples of behaviors that are the opposite of showing out would be listening carefully, being polite, showing respect, or acting in a manner that is appropriate for the situation. In essence, antonyms for showed out would be words that describe behaving in a manner that is not overly attention-seeking but instead reflects maturity and good judgment.