To be able to last through and handle the good times as well as the bad times. (Usually in the sense of a relationship of sorts). Thick is representative of the good times, whereas thin is representative of the bad times.
True lovers will stick together through thick and thin.

My best friend and I have been through thick and thin and are still as close as we ever were.
by spacekittens246810 December 22, 2013
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through the good times and the bad times thick being bad and thin being good. fuck all you bitches
throgh thick and thin, if something is THICK then it is HARD to get through. If something is THIN it is EASY to get to. through thick and thin definition= throguh the bad and the good.
by Sasasasandbom May 16, 2019
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