1. To jump from Wikipedia entry to Wikipedia entry through related links until you've ended up on a subject completely unrelated to the subject you started with, e.g., starting at socioeconomics and ending at Carrot Top.
2. Similarly, in a conversation, jumping from topic to topic until neither party remembers what subjects led them to the final topic.
Sarah: "Good lord. How did I carrot-top from Lindsay Lohan to the Hanshin earthquake in Japan?"
Mark: "...and so obviously Kara Thrace was an angel sent from the one true God--"
Abby: "Hold it. Back up. We've totally carrot-topped from what to get for Beth's baby shower."