A gutter is the channel or trough that runs along the edge of a roof or street to collect and carry away water. When rain falls on your house, it flows down the roof into gutters that direct it away from the foundation. Street gutters are the low concrete channels along curbs where rainwater flows toward storm drains. Without gutters, water would pour straight down the sides of buildings or flood across sidewalks.

The word also describes the groove on either side of a bowling lane, where balls roll when they miss the pins. When your ball goes into the gutter instead of hitting the pins, it's called a gutter ball. Some bowling alleys put up gutter guards (bumpers) for younger players, so every ball reaches the pins.

Sometimes people use gutter to describe rough, unpleasant things. If someone says a conversation dropped into the gutter, they mean it became crude or inappropriate. Gutter can suggest something low, dirty, or degraded, like the way water and debris flow through street gutters. A newspaper might be called the gutter press if it focuses on scandal and gossip rather than serious reporting.