Rapping (also rhyming, flowing, spitting, emceeing, or MCing) is an artistic form of vocal delivery and emotive expression that incorporates "rhyme, rhythmic speech, and [commonly] street vernacular". It is usually performed over a backing beat or musical accompaniment. The components of rap include "content" (what is being said, e.g., lyrics), "flow" (rhythm, rhyme), and "delivery" (cadence, tone). Rap differs from spoken-word poetry in that it is usually performed off-time to musical accompaniment. It also differs from singing, which varies in pitch and does not always include words. Because they do not rely on pitch inflection, some rap artists may play with timbre or other vocal qualities. Rap is a primary ingredient of hip-hop music, and so commonly associated with the genre that it is sometimes called "rap music".

Precursors to modern rap music include the West African griot tradition, certain vocal styles of blues and jazz, an African-American insult game called playing the dozens (see Battle rap and Diss), and 1960s African-American poetry. Stemming from the hip-hop cultural movement, rap music originated in the Bronx, New York City, in the early 1970s and became part of popular music later that decade. Rapping developed from the announcements made over the microphone at parties by DJs and MCs, evolving into more complex lyrical performances.

Rap is usually delivered over a beat, typically provided by a DJ, turntablist, or beatboxer when performing live. Much less commonly a rapper can decide to perform a cappella. When a rap or hip-hop artist is creating a song, "track", or record, done primarily in a production studio, most frequently a producer provides the beat(s) for the MC to flow over. Stylistically, rap occupies a gray area between speech, prose, poetry, and singing. The word, which predates the musical form, originally meant "to lightly strike", and is now used to describe quick speech or repartee. The word has been used in the English language since the 16th century. In the 1960s the word became a slang term meaning "to converse" in African American vernacular, and very soon after that came to denote the musical style.

Rap music has played a significant role in expressing social and political issues, addressing topics such as racism, poverty, and political oppression. By the 21st century, rap had become a global phenomenon, influencing music, fashion, and culture worldwide.

The English verb rap has various meanings; these include "to strike, especially with a quick, smart, or light blow", as well "to utter sharply or vigorously: to rap out a command". The Shorter Oxford English Dictionary gives a date of 1541 for the first recorded use of the word with the meaning "to utter (esp. an oath) sharply, vigorously, or suddenly". Wentworth and Flexner's Dictionary of American Slang gives the meaning "to speak to, recognize, or acknowledge acquaintance with someone", dated 1932, and a later meaning of "to converse, esp. in an open and frank manner". It is these meanings from which the musical form of rapping derives, and this definition may be from a shortening of repartee. A rapper refers to a performer who "raps". By the late 1960s, when Hubert G. Brown changed his name to H. Rap Brown, rap was a slang term referring to an oration or speech, such as was common among the "hip" crowd in the protest movements, but it did not come to be associated with a musical style for another decade.

Rap was used to describe talking on records as early as 1970 on Isaac Hayes' album ...To Be Continued with the track name "Monologue: Ike's Rap I". Hayes' "husky-voiced sexy spoken 'raps' became key components in his signature sound". Del the Funky Homosapien similarly states that rap was used to refer to talking in a stylistic manner in the early 1970s: "I was born in '72 ... back then what rapping meant, basically, was you trying to convey something—you're trying to convince somebody. That's what rapping is, it's in the way you talk."

It is sometimes claimed that “rap" is an acronym for 'Rhythm And Poetry', but this does not reflect the history of the word and thus is best seen as a backronym.

Similarities to rapping can be observed in West African chanting folk traditions. Centuries before hip-hop music existed, the griots of West Africans were delivering stories rhythmically, over drums and sparse instrumentation. Such resemblances have been noted by many modern artists, modern day "griots", spoken word artists, mainstream news sources, and academics. Rap lyrics and music are part of the "Black rhetorical continuum", continuing past traditions of expanding upon them through "creative use of language and rhetorical styles and strategies".