What is Lullaby in the poem "Lullaby"?

A lullaby is a song or folk poem meant to help a child fall asleep. The following definition of the term “lullaby” is reprinted from A Poet's Glossary by Edward Hirsch. A bedtime song or chant to put a child to sleep. W H Auden's 'Lullaby' is an unconventional love poem, celebrating the impermanence and physicality of erotic love.