1. responded to a situation or stimulus with a particular action or emotion
Usage: past tense of react
2. underwent a chemical change when combined with another substance
Usage: chemistry; past tense of react

Examples

• She reacted angrily to the news.
• The audience reacted with loud applause.
• He reacted quickly to avoid the accident.
• The metal reacted with the acid to produce gas.
• They reacted positively to our proposal.
• The chemical reacted violently when heated.
• She reacted by walking out of the room.