A stanza of four lines in poetry is called a quatrain. The word "quatrain" comes from the French word "quatre," meaning "four." A quatrain is a common type of stanza used in various forms of poetry, including sonnets, ballads, and odes. It typically consists of four lines with a specific rhyme scheme and meter. Quatrains can be written in a variety of styles, such as alternating rhyme or enclosed rhyme, and can be used to convey different themes and emotions depending on the poem's context.