Uninteresting and prolonged jizz, cum, ejaculate, sperm or semen when the man ejaculates after a long time of no sexual activity that does not involve friction on the male genitals thus, causing no heat. Therefore the ejaculate is cold and clumpy.
Originated from Yelawolf's new song "Good Girl" (ft. Poo Bear) on his new album "Radioactive":
"But you don't wanna see me go/Even though I'm only giving you dick and cold cereal/So you must have a thang for Lucky Charms/All the bad girl in you just fell in my lucky arms"
Bro #1: Bro, last night I gave her a bowl of 'cold cereal' because all we did was oral sex and ended it with a long make out session.
Bro #2: Sucks for her (no pun intended)