Meaning of “rack” - Learner’s Dictionary

rack

verb us uk /ræk/
be racked with pain/guilt, etc

If someone is racked with pain or an emotion, they suffer a lot because of it.

rack your brain/brains informal

to think very hard, usually to try to remember something or solve a problem

See also

(Definition of “rack verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)