You know those little pieces of hard, white stuff in ground beef? It's called gristle.
Sure, you've heard that before, but what the heck is gristle?
Smooth, solid, and elastic, it's the stuff that makes your ears hold their shape but remain flexible, and it's what most of your nose is made of.
Cartilage in the nose.
(Diagram from the Free Dictionary)
Your larynx (a.k.a. voice box) is made of cartilage. Your xiphoid process (a.k.a. sternum) is made of cartilage. Cartilage also covers the ends of any bones where they meet at bendable joints.
Cartilage is also what an embryo's skeleton is made of and as the embryo matures, the cartilage becomes bone.
You've probably encountered cartilage / gristle when you've cleaned chicken parts. It's the knobby white stuff that isn't as hard as bone and it's sure not meat.
Cartilage, or gristle, in a chicken thigh.
(Photo from Home Ec 101)
Apparently, when the hard-working butchers are grinding up the cow to make ground beef, they aren't as careful to remove all the cartilage. So it gets ground up along with everything else and then much later, you discover it as a little knobbly white thing in your hamburger.
By the way, if you search for the word "gristle," or images of gristle, you'll find a lot of references to and pictures of Madonna. This is because her ex-husband, Guy Ritchie, said that her four-hour-per-day workout regimen pared her down to such an extent that trying to be romantic with her was like "cuddling up to a piece of gristle."
Obviously Guy Ritchie was angry about a lot of things, but there are a lot of photos of Madonna out there in which her arms are pretty scary-looking.
(Photo from the Telegraph, sourced from Home Talk Entertainment where you can see some even less flattering photos)
Webster's 1828 dictionary, gristle
Online Etymology Dictionary, gristle
Medical Free Dictionary by Farlex, cartilage (redirected from gristle)
Daily Mail, "Making love to Madonna 'was like cuddling up to a piece of gristle,'" October 20, 2008