Heroin. As contrasted with white pony, slang for cocaine, in the 1983 pop hit "White Horse" by music group "Laid Back".
"If you want to ride, don't ride the white horse."

"The TV Show 'Twin Peaks' used a white horse to symbolize heroin addiction."
by hackerb9 November 4, 2007
Alex has been riding the white horse for days now, hes bound to fall off soon.
by The Horse Whisperer May 3, 2004
heroin ,another term for heroin
if you want to ride dont ride the white horse (heroin)
if you want to ride, ride the white pony (cocaine)
by cocaine/heroineHeadrushBabe November 25, 2006
Linked to instinct, purity and the drive of the physical body to release powerful and emotional forces, like rage with ensuing chaos and destruction. Most notably from Rob Zombie's Halloween 2.
Guy: Why is he killing everybody?

Other Guy: He has visions of a white horse.
by Jmanbandit September 6, 2009
Street Definition for Cocaine Methamphetamine, and Heroine
Riding the white horse means to be high off one of these substances listed above
by Barz the Phoenix April 25, 2016
In a relationship, when the couple fights and breaks up, the girl will usually refer to the guy's charm in getting her back as his white horse.
"It's too late for your white horse to come around."
by Pencilcharm April 3, 2010