In the military this refers to creamed chipped beef on toast.
In the Southern US, a similar dish is made consisting of chunks of fried ground beef in a thin cream gravy, served over toast. It is associated with poverty, because it is cheap, packed with calories, and filling.
"Naw, we're out of PET milk, somebody's gonna hafta go ta the store."
To be used when in online discussion and another party (whom you do not want to see anything suspicious being sent from the partner(s) you are having the conversation with)
Useful when the parent walks in and then there is no need for suspicious minimizing on the computer screen.
Tim: Oh baby, i'm in the mood ;)
---Tiff's father walks in---
Tim:Ok, so, about the science homework due tomorrow....