Nuking the
fridge is simply the act of creating more storage space in your cold storage unit, and/or saving money; by eating all the leftovers which are starting to get... bigger.
In many locations, heating something in a
microwave is called 'nuking' it - due to a poor understanding of the structure of the electromagnetic spectrum.
Similarly in many locations the word refrigerator is shorted to 'fridge'.
Thus from the combination, we get 'nuke the fridge' - to heat up chilled leftovers from your fridge, in a
microwave. It's not complicated, not should it be.
"I'm too knackered to
cook tonight, you wanna go out?"
"Nah, I'm too povvo this week,
maybe we should just nuke the
fridge."