Pink slime is meat made by pressure-spraying to blast off any remaining scraps from existing cuts. Mechanically-separated chicken is made by blasting chicken scraps. Nearly all meat in frozen pizzas is created by gluing together mech-sep scraps.

When you use that process, you do not always get only the meat but also various other tissues. We probably get fed 0.0002% pig anus but hey, as long as it's cooked to 160 degrees F, some government guy says it's okay.