The place where you put things when your
pdl is full. If
you don't have one and too many things get pushed, you forget
something. The overflow pdl for a person's memory might be a
memo pad. This usage inspired the following doggerel:
Hey, diddle, diddle
The overflow pdl
To get a little more stack;
If that's not enough
Then you lose it all,
And have to pop all the way back.
--The Great Quux
The term
pdl seems to be primarily an
MITism; outside MIT
this term is replaced by "overflow
stack".