This phrase is mentioned several times on Roderick on the Line and is an inside-joke between John and Merlin that probably originates from a tweet from 2010-03-31:

"I put on my Live Genesis record to help me clean my house, but instead of cleaning I built a seven-sided magic lighthouse out of dreams." — @johnroderick

The meaning is difficult to explain, but it probably means that John is daydreaming and building himself a seven-sided lighthouse made out of dreams inside his head instead of doing what he is supposed to be doing, which is often a very practical and straight-forward task.

This was interestingly on the same day when John had his first Twitter-interaction with Aimee Mann (RL275) and three weeks after he won the Tweet of the Year as part of the Seattle Weekly's Best of the Web 2010. (see Awards). (RL187, RL270)

Sections where the term is used: