A phrase used to indicate that one or something is finished, complete, or no longer able to continue. Alludes to the practice of testing how thoroughly a piece of meat is cooked by piercing it with a fork. Barbara: "Johnny, would you like any more of this cake?" Johnny: "No thank you, Barb. You can stick a fork in me, I'm done!" I'd say we just need one more week on the project, and then you'll be able to stick a fork in it!