1. a group of four people who sing or play music together
2. a piece of music written for four voices or instruments
3. any group or set of four people or things

Examples

• The string quartet performed Beethoven’s music beautifully.
• She joined a jazz quartet that played at local clubs.
• The composer wrote a quartet for two violins, viola, and cello.
• Mozart’s quartets are considered masterpieces of classical music.
• A quartet of friends decided to start a business together.
• The barbershop quartet sang harmonies at the festival.
• The book features a quartet of stories about friendship.