1. A device that automatically switches an electric lamp off and on, as in a commercial display sign.
2. Slang. One who engages in indecent exposure; an exhibitionist.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.