A person that responds to an emergency situation or other calling.(noun)
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Use "responder" in a sentence
""A responder is someone who does what is right, whether anyone is looking or not," King said."
"When I called the responder's voice sounded a bit deep."
"As a preschool teacher for about 6 years I will tell you that the previous responder is right, a child’s eating pattern can change drastically when they are not around mom and dad."