There are 2 results of your search for Billy.
Billy
A surfer from Bankstown. A place not known for producing good surfers. "Billy Bankstowner": He was a bit of a Billy. (i.e. could not surf very well). He surfs like a Billy.
billy
A bong: pack us another billy.
Contributor's comments: I grew up in Greystanes (west subs of Sydney) where a billy was a bong ('billybong'). "Goin' back for a few billys" was a well used phrase back then.