Guess I was 64% right.
http://gizmodo.com/5742413/this-is-what-really-hides-in-taco-bells-beef
http://gizmodo.com/5742413/this-is-what-really-hides-in-taco-bells-beef
According to the USDA, you can't call this "beef" at all. Beef is defined as "flesh of cattle". Ground beef is defined as:Chopped fresh and/or frozen beef with or without seasoning and without the addition of beef fat as such, shall not contain more than 30 percent fat, and shall not contain added water, phosphates, binders, or extenders.