From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Cloning (分身, Bunshin) is a supportive technique used by many fighters. The user splits into several identical duplicates of themselves to fight as a group.
Cloning appeared quite often in the anime, but the only manga usage was Tenshinhan's Shishin-no-ken and Dragon Ball: Ossu! Kaette Kita Son Goku to Nakama-tachi!!.
 Dragon Ball
 Dragon Ball Z
Piccolo and Kuririn each used the Tri-Form in their battle against Vegeta and Nappa. This was similar to the Shishin-no-ken used by Tenshinhan. While Fusion techniques seemed to do the exact opposite, it was unknown how they acted together (for example, if Piccolo could split into his former self and Nail).
Abo and Kado used this technique in their fight against Son Goten and Trunks Brief in Dragon Ball: Ossu! Kaette Kita Son Goku to Nakama-tachi!!.