Definition of responder in US English:

responder

noun

  • See respond

    • ‘I asked responders to recall their best and worst times on this annual night.’
    • ‘Most cities do not have the necessary equipment to determine what kind of hazardous materials emergency responders may be facing.’
    • ‘The emergency responders discovered a home laboratory containing bacteria samples, petri dishes and equipment to analyze DNA.’
    • ‘Our emergency responders are probably better equipped and better trained than at any other time in history.’
    • ‘Even when so-called placebo responders are dropped from a study, a good proportion of the remaining patients respond to placebos anyway.’