Stack
Stack turns up in 2 fields: vacuum, printing. Here is what it means to the people in each one.
Stack in vacuum
Shop name for the whole column of high vacuum pump, valves, trap and backing line that pumps a chamber.
The assembly under or beside a chamber: high vacuum valve, baffle or trap, high vacuum pump, foreline valve and backing pump. Diffusion pump systems in particular are sold and rebuilt as stacks. Talking about the stack rather than the pump keeps attention on the whole gas path, since a tired stack often has its weak link in a valve or trap rather than in the pump itself.
"Pull the whole stack, rebuild the diff pump, clean the baffle and put new O-rings on every valve."
Stack in printing
Excessive ink building up on press rollers or blankets.
A condition where ink builds up excessively on the rollers, blanket, or printing plate instead of transferring cleanly to the paper. This happens when the ink is too tacky, dries too fast on the press, or when running highly pigmented inks without enough vehicle. It leads to poor print quality, mottled solids, and can eventually pull fibers off the paper.
"The magenta is starting to stack on the second unit, so we need to add a little reducer."