1. One of the bony, permanent, hollow paired growths, often curved and pointed, that project from the upper part of the head of certain mammals, as cattle, sheep, goats, or antelopes.
2. A synonym for penis, named after the similarities to the first definition. Both are hard, permanent, curved and pointed.
3. An instrument for making a noticeable sound, often used on vehicles such as cars, motorcycles, bicycles, etc.
4. A trumpet.
5. A symbol of power or strength.
Bob: "I saw his huge animal with horns on the road, so I instinctively honked on the horn while putting some pressure on the breaks. I stopped a few inches short of it--the bastard didn't move the whole time--and hopped out to lecture it on road safety. It looked so cute that I whipped out my horn and began making anal love to it, while I belched out some notes from a horn I always carry around with me--yeah, I'm kinky like dat!
Jim: Dude... you are the greatest horn in history!