The abnormally large reproductive organ of an exceptionally well hung man, reminiscent of the extended piece of a horse due it's rather unusual shape and size, otherwise also referred to as a macropenis.
A higher class of curse word, used only by intellectuals. A phrase used only when something really crappy has just happened, so you know to treat the situation with the up most urgency. If one utters, “horse cock” you know that they got screwed out of nowhere.