Pink slime is "ammoniated boneless lean beef trimmings or similar products, which are considered "unfit for human consumption" until ammonia has been added." -Grant Roberts (http://www.unifiedlifestyle.com/blog/2011/07/19/is-usda-approved-ground-...)
McDonald's has recently removed pink slime for burgers, but the USDA has recently approved it for school use.
http://www.nbc11news.com/news/headlines/Whats_in_your_students_school_lu...