When you take a dip (perferably grizzly) and you insert two sperate dips on each side of your lower lip leaving the middle part of your lip dip free thus having a "wall"
When you are losing an argument and need to derail the conversation, you suddenly bring up the Berlin Wall. The irrelevance throws the other person off, and you can twist their response to make it look like you won.
Example:
A heated argument is going on.
Person A: "Yeah but here’s the thing, the Berlin Wall."
Person B: "What does that have to do with anything?"
Person A: "Oh, so you hate people who want to reunite with their family?"
Person B: "No…"
Person A: "Exactly."
Victory.