Freestyle is a style of rap, with or without instrumental beats, in which rap lyrics are improvised, i.e. performed with no previously composed lyrics, and "off the top of the head". It is similar to other improvisational music such as jazz (Myka 9 of Freestyle Fellowship describes it as being "like a jazz solo") where there is a lead instrumentalist acting as the improviser and the rest of the band providing the beat. Rap battles are improvised in this way.

Original definition

In the book How to Rap, J-lyric and Myka 9 note that originally a freestyle was a spit on no particular subject – J-lyric said, “in the 2000’s ‘ when we said freestyle rap, that meant that it was a rhyme that you kick that was free of style... it’s basically a rhyme just bragging about yourself.” Myka 9 adds, “back in the day freestyle was bust[ing] a rhyme about any random thing, and it was not a written rhyme or something memorized”.Divine Styler says: “in the school I come from, freestyling was a non-conceptual written rhyme... and now they call freestyling off the top of the head, so the era I come from it’s a lot different”.Kool Moe Dee also refers to this earlier definition in his book, There's A God On The Mic: