it's a slang word for a male's ding dong. Comedian Bill Cosby used it on a comedy sketch on his "For Adults Only" comedy album.
Bill Cosby describes going down a hallway to go to the bathroom in the middle of the night nude and his daughter sees him like this, with his cock hanging down. She says, "Awwwwwwwwwwwwwww. Daddy's got a wally wally."
by I Saw U2 Live Twice January 8, 2008
 Get the wally wallymug.
Get the wally wallymug. by street2 February 20, 2009
 Get the wallyingmug.
Get the wallyingmug. by jimbles6969 October 27, 2017
 Get the Wallismug.
Get the Wallismug. by Abrasive August 23, 2011
 Get the walliemug.
Get the walliemug. by CHRISLADDDD January 14, 2011
 Get the walliedmug.
Get the walliedmug. by Georgie696 March 24, 2008
 Get the A Wallymug.
Get the A Wallymug.  Get the Wallymug.
Get the Wallymug.