The Bedford Glossary of Critical and Literary Terms - Ross Murfin 2018
Quatrain: A stanza containing four lines. The term is also used, though less commonly, to refer to a four-line poem. No rhyme scheme need exist in a quatrain, but the following rhyme schemes are common: abcb (the ballad stanza), abba, and abab. The quatrain is the most common stanzaic form in English-language poetry.
EXAMPLES: Persian poet Omar Khayyám’s Rubáiyát (c. eleventh—twelfth century), translated into English by Edward Fitzgerald and published in 1859 as the Rubáiyát of Omar Khayyám, contains about five hundred epigrammatic rubáiyát, or quatrains, rhyming aaba. Many of William Blake’s Songs of Innocence and of Experience (1789—94) are composed in quatrains; “Infant Sorrow,” for instance, has an aabb rhyme scheme and begins:
My mother groan’d! my father wept.
Into the dangerous world I leapt.
Helpless, naked, piping loud;
Like a fiend hid in a cloud.
Josephine Miles often used unrhymed quatrains, as in this example from her poem “Belief” (1955):
Mother said to call her if the H-bomb exploded
And I said I would, and it about did
When Louis my brother robbed a service station
And lay cursing on the oily cement in handcuffs.