A gutter is a pipe or trough along the edge of a roof that carries rainwater away from a building. Another kind of gutter is the indentation beside a street curb. Water flows through these gutters too, usually into a storm drain.
The purpose of the gutters on a roof is to prevent water damage to a structure or flooding around its foundation. A gutter directs the flow of rainwater away from the house, often into a drain or rain barrel. There are other kinds of gutters, too, like the gutters that drain water on the edge of a street and the gutters on the sides of a bowling lane. As a verb, gutter means "to flicker or burn unsteadily," like a candle in the wind.