What do you call a stanza that consists of three lines?

A stanza that consists of three lines is called a tercet. This term is derived from Italian poetry, where "terza" means three. Tercets are often used in various forms of poetry and can have different rhyme schemes.

Understanding what a tercet is can enhance your appreciation for the structure and rhythm of poetry. It is helpful to recognize not only the definition but also how tercets fit within different poetic styles and forms, such as in a villanelle or when employed as part of a larger poem.