When two or more drivers can't physically argue with one another, the exchange is verbalized with their car's horns.
Example 1.
Driver A hesitates for a moment after the traffic light changes green, prompting Driver B to honk his horn. Driver A is offended because just as he was starting to move, that jerk behind him blew his horn, or as in some cases, Driver A simply doesn't like being honked at, so Driver A honks back. Driver B is offended because Driver A didn't have a right to honk back, so Driver B honks with sarcasm. Now, Driver A is really upset because usually by this time both cars are moving, and if possible, Driver B has pulled alongside Driver A to curse, flip the bird, etc., at that time becoming a roadrage, because in a genuine hornfight, no words or gestures are exchanged.

Example2.
Again, Driver A hesitates after the light has changed green. Driver D initiates the sequence with a long hard sarcastic honk, because Drivers B&C are obviously not paying attention either. After making Drivers B&C aware, they decide to lean on their horns, adding to the noise, infuriating Driver A, who honks his horn like a frothing madman because the anxious idiots behind him don't hear the siren on the emergency vehicle that he can see coming, to make the wise choice of letting it approach instead of bolting out in front of it, possibly causing an accident.
by Worldhead October 22, 2009
Get the hornfight mug.