British slang for a sudden, clever idea. Similar to the American "brainstorm." Often used sarcastically.
Suzie invited the neighbors in to see her most recent brainwave, a water fountain in the middle of her living room.
by RayWestlake February 3, 2008
by rperazag May 23, 2010
by SomeoneNew August 6, 2011
When you are receiving oral pleasure (fellatio) and when you are about to blow your wad, you cum in her nose which feels like when you dive in a pool incorrectly and all that water gets into your sinuses and hurts, thus the name brainwave.
Dude, I was getting blown by Jessica and i just felt like giving her a brainwave, she passed out, then I gave her another one.
by Retoric June 14, 2008