Usually occurs during a bout of food-poisoning or a night on the beers which can lead to severe pains and abnormalities relating to excretion. Upon going to the toilet for a dump, rather than fall vertically from your backside it will spray, or release horizontally. Called 'doing a horizontal'.
Person 1: "hey do you know how i remember the word horizontal?"
Person 2: "No, how?"
Person 1: "Because whores are always on their back"
By Kerstin
Horizontal
The state assumed by some people for up to 15-20 hours a day. It is the opposite of being vertical and consists of sleeping, laying down, general inactivity and lack of motivation to do anything.