IPA: /ˈriːˌteɪkər/
KK: /ˈriːˌteɪkər/
A person who takes something again, often used in the context of exams or tests.
After failing the exam, she became a retaker and studied hard for the next attempt.
Retaker → It is formed from "re-" (meaning again) and "take" (from Old English "tacan", meaning to seize or grasp) and "-er" (meaning a person who). The word "retaker" refers to a person who takes something again.
Think of someone who is 'taking' ('take') something 'again' ('re-') — that's why a retaker is someone who takes something again.