Underreactive

Part of speech: adjective

Definitions

1. Exhibiting insufficient or delayed response to stimuli or situations; showing a lack of appropriate reaction or emotional intensity; demonstrating a subdued or muted effect when action or feeling is expected
2. Characterized by a lower than normal level of responsiveness to external or internal triggers; presenting a minimal or inadequate expression of emotion or action; reflecting a restrained or diminished reaction in contexts usually evoking stronger responses
3. Describing behavior or processes with less sensitivity or activity than typical; indicating a failure to respond fully or with suitable force in circumstances; conveying a tone of understatement in reactions or feelings compared to what is anticipated

Etymology: "Under-" is one of English's most productive prefixes, and "underreactive" is a plain formation rather than a story with a famous coiner. It combines the prefix "under-", meaning "below a normal level or degree", with "reactive", itself built from "react" and the suffix "-ive". "React" came into English in the seventeenth century from Latin "reagere", meaning "to act back", with "re-" signifying return and "agere" meaning "to do" or "to drive". The sense has moved from chemistry into medicine and psychology. "Reactive" was first used of chemical substances that readily undergo reaction, and later of organisms, tissues and people who respond readily to stimuli. Adding "under-" flips the emphasis: where "reactive" describes a readily responding system, "underreactive" describes one that responds less than expected, whether a nervous system dulled by a drug or a person whose feelings seem muted for the situation.

Synonyms: unresponsive, insensitive, apathetic, unreactive

Antonyms: overreactive, hyperreactive, responsive, sensitive