"Beef trimmings" refers to the small pieces of meat that are cut off during the process of preparing or trimming a larger piece of beef. Full definition
In his original post on The Daily, David Knowles reported that «USDA... plans to buy 7 million pounds of Lean Beef Trimmings from BPI in the coming months for the national school lunch program,» and I and other media outlets shared the same information, i.e., that a purchase of slime per se was in the works. (thelunchtray.com)
It is made with an assortment of beef trimmings whose fat is separated through heat and the use of a centrifuge. (articles.chicagotribune.com)
«Lean, finely textured meat» made from beef trimmings is often added to ground beef as a cheap filler (npr.org)