According to dictionary.com it is "a flexible pipe for conveying a liquid or gas."

While thats technically correct, the only way I've heard it used is in reference to what most people would call a garden hose. You know, that thing on the outside of a house you use to water the grass?

Its just one of dem Southern things, y'all. (In the United States that is. I'm not sure about other countries.)

Update: Zerotime says the word is also used in England.

A woman appeared on the news the other day protesting angrily about a hosepipe ban being introduced by the water company in her area. She is a prize-winning gardener who has won many awards following her passion and is, apparently, quite highly respected in her field. Now she will be unable to water her prized blooms with a hosepipe and, instead, may have to actually carry a watering can from tap to plant, to plant to tap.

Yesterday in Ethiopia a mother killed her baby with diseased water. Luckily there is no hosepipe ban in force in her village.