"Defrosted lemons" is a term used to describe a parchingly refreshed feeling someone gets from any event. Usually the subject whose "lemons" are being "defrosted" are in between the two words.
When my friend does something mildly impressive, you could say:
"Oh wow, that totally defrosted my lemons", or "You really just defrosted lemons, damn".
A sour situation made even worse.
She broke up with me, and then revealed that she had given me syphilis. What a defrosted lemon.