A limerick is a kind of a witty, humorous, or nonsense poem, especially one in five-line anapestic or amphibrachic meter with a strict rhyme scheme (aabba), which is sometimes obscene with humorous intent. The form can be found in England as of the early years of the 18th century. It was popularized by Edward Lear in the 19th century, although he did not use the term.

The origin of the name limerick for this type of poem is debated. As of several years ago, its usage was first documented in England in 1898 (New English Dictionary) and in America in 1902, but in recent years several earlier uses have been documented. The name is generally taken to be a reference to the City or County of Limerick in Ireland sometimes particularly to the Maigue Poets, and may derive from an earlier form of nonsense verse parlour game that traditionally included a refrain that included "Will [or won't] you come (up) to Limerick?"

The standard form of a limerick is a stanza of five lines, with the first, second and fifth usually rhyming with one another and having three feet of three syllables each; and the shorter third and fourth lines also rhyming with each other, but having only two feet of three syllables. The defining "foot" of a limerick's meter is usually the anapaest, (ta-ta-TUM), but limericks can also be considered amphibrachic (ta-TUM-ta).

However, from a rhythmic point of view, lines 1, 2 and 5 have a silent accent at the end, making 4 accents per line. Lines 3 and 4 combined also have 4 accents, making four lines with an overall total of 16 accents (i.e. foot tapping "beats" ). This is why limericks can be sung to sixteen bars of 3/4 music. Reading, or reciting, naturally follows the faster rhythm of 6/8 time, making eight bars of two triplets per bar. A triplet represents a "foot" of 3 syllables.

The first line traditionally introduces a person and a place, with the place appearing at the end of the first line and establishing the rhyme scheme for the second and fifth lines. In early limericks, the last line was often essentially a repeat of the first line, although this is no longer customary.
Within the genre, ordinary speech stress is often distorted in the first line, and may be regarded as a feature of the form: "There was a young man from the coast;" "There once was a girl from Detroit…" Legman takes this as a convention whereby prosody is violated simultaneously with propriety.

Exploitation of geographical names, especially exotic ones, is also common, and has been seen as invoking memories of geography lessons in order to subvert the decorum taught in the schoolroom; Legman finds that the exchange of limericks is almost exclusive to comparatively well-educated males, women figuring in limericks almost exclusively as "villains or victims". The most prized limericks incorporate a kind of twist, which may be revealed in the final line or lie in the way the rhymes are often intentionally tortured, or both. Many limericks show some form of internal rhyme, alliteration or assonance, or some element of word play.

Verses in limerick form are sometimes combined with a refrain to form a limerick song, a traditional humorous drinking song often with obscene verses.