A quote pyramid occurs when someone on a forum quotes someone else's post who has quoted someone else who quoted someone else etc. etc. .
If the forum does not have something that automatically caps the amount of quotes in one post, then this results a huge pile-up of quotes in a series of different posts. These, are Quote Pyramids.
Dude 1:Oh man there was a post with over 1000 quotes in the other day, biggest quote pyramid I've ever seen.
Dude 2: Orly?