a good idea.

derived from classic cartoons when the characters have a lightbulb appear above their head when they have an idea.

Is a person who is an absolute dimwit.Used in Liverpool,UK.Can be used when they are also useless in most every day scenarios.

n. A light bulb, although usually used for lamps and such, can be used to smoke meth.

General term for well meaning but unreliable person, often intelligent but prone to lapses in concentration and brain function.

The head of a circumsized erect penis if of greater girth than the shaft.

A small, 1 serve cannister of Nitrous Oxide used for getting a kinda fun, but quite pathetic 5 minute high.
Possibly puts bubbles in your brain.

A bulb is somebody who has difficulty forming thoughts and sentences on his own, yet insists on doing so on a public forum.

(by @cgawker on Twitter)