A respondent is a person who gives an answer. For example, on some Monday mornings, your teacher might feel like she is talking to the walls — although she asks questions, none of the sleepy students are willing respondents.
A respondent is a person who answers a question, letter, email message, survey, or anything else that requires a response. You can see the word respond, which means "answer or reply to" in respondent. If a poll reveals that bullying is the top concern regarding school safety, you know that many respondents checked the box marked "bullying."