1. responding to a stimulus, situation, or treatment
Usage: present participle of react
2. undergoing a chemical reaction
Usage: chemistry

Examples

• She is reacting badly to the medication.
• The crowd was reacting with cheers and applause.
• He’s still reacting to the shocking news.
• The chemicals are reacting to form a new compound.
• The patient is reacting well to treatment.
• I’m reacting too emotionally to this situation.
• The metal is reacting with the acid.