Q: What do you call a cow with two legs?
A: Lean meat!
Explanation: For some reasons I find cows to be funny, like this joke.
When something leans it is not quite straight up and down, it is a tilted like the Leaning Tower of Pisa or Leaning Cow Wine. If a cow had only two legs it would, at a minimum, lean; most likely it would fall over.
Lean meat is meat is meat that does not have much fat.
This joke is funny because it plays with two meanings of the word lean.
By the way, askew means crooked. Try a Google search for the word askew and see what happens to the screen!
…and just so you know, the Leaning Tower of Pisa is not leaning as much these days: