The term "overemotional" refers to someone who is excessively high-strung or prone to irrational outbursts. Antonyms for this descriptor include "unemotional," "detached," "apathetic," and "dispassionate." These words typically connote a lack of emotional expression or sensitivity, and are often associated with personalities that are calm, collected, and rational. Other possible antonyms for "overemotional" might include "composed," "equable," "stoic," "unflappable," or "self-possessed." Depending on the context, these different terms may be more or less appropriate for describing a person who is not prone to emotional extremes.