Definitions

1. adjective

tending to react or respond readily and often strongly to a stimulus or situation.

“The student was highly reactive to criticism, often becoming defensive.”

2. noun

a substance that reacts with another substance to form a new compound.

“The lab technician handled the reactive chemicals with caution.”

3. noun

a person who is prone to reacting strongly or emotionally to situations.

“He’s a very reactive person and gets upset easily.”