In music, a trill is a rapid alternation between two adjacent notes, creating a fluttering, shimmering sound. A flutist playing a trill quickly switches back and forth between two notes so many times per second that they blur together into something that sounds almost like a bird's song. In classical music notation, a trill is marked with “tr” above a note, telling the musician to add that special wavering ornament.

Many birds naturally trill when they sing. A canary's song includes beautiful trills that rise and fall. When you hear a robin in spring, those liquid, rolling sounds often include trills.

The word also describes any similar quavering sound. Your voice might trill when you roll your Rs in Spanish, making your tongue vibrate rapidly. Some languages use trilled Rs as standard pronunciation. A phone's ring might trill, and you might hear the trill of insects on a summer evening.

People sometimes use trill to mean singing or speaking in a high, cheerful, bird-like way: “She trilled with delight when she saw the surprise party.”