Trill/trɪl/ Definition 1 of 4Pro Tip 1/2Vocal Expertise The verb 'trill' often indicates a singer's skill to rapidly shift pitch. The opera singer was able to trill effortlessly. Pro Tip 2/2Birdsong Description 'Trill' commonly describes bird sounds, suggesting a pleasant and natural quality. Awakening in the forest, I listened to the birds trill.