Learn how to say Callback correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word callback:
1an invitation to return for a second audition or interview:
he was one of only twelve applicants to receive a callback
2a telephone call made to return one that someone has received.
3 [mass noun] a security feature used by some computer systems accessed by telephone, in which a user must log on from a previously registered phone number, to which the system then places a return call.