Any of the hordes of rednecks, rubes, and other
undesirables that infest the rural areas of the country. It is a
combination of the words "hick" and "dickhole."
Essentially, it refers to a younger hick who has done or is about to do something to piss you off (i.e. swerve into your lane while reaching for a beer, spit tobacco juice on your lawn, blare 80's rock on a shitty boombox outdoors at 8am on Sunday while washing his Firebird, etc).