Wiktionary
hard head
n. (context two-up English) A crooked organiser of a two-up game, who would cheat players out of their money.
Wikipedia
Hard Head
Hard Head is a 1988 arcade platform game made by SunA corporation. In the game, players control the title character, who must traverse a set of levels by defeating enemies with a bubble gun.
Usage examples of "hard head".
But it was TT who rubbed a hard head against her shoulder, then stopped between Telzey and the bushes on their right, back rigid, neck fur erect, tail twisting.