A person who lacks the ability to hold a conversation (most commonly in texting or online). These one-dimensional people use emotionless phrases such as, "okay," "haha," and "yeah," forcing any attempt at conversation to hit rock bottom, thus appearing as though you are talking to a wall.
Jake: Are you going to that party tonight?! :D
Jake: Okay sweet! Let's get plastered! :)
Jake: We can be pong partners..?
Tom: Any progress with Lindsey?
Jake: Nah, she's being a wall-person again.