From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Regeneration (再生, Saisei; Literally meaning "Reproduction") is a supportive technique used by many fighters. The user replaces any limb lost in battle and recovers from similar severe damage.
Most Namekians were able to use Regeneration. Regeneration first appeared at the 23rd Tenkaichi Tournament after Son Goku redirected Piccolo's own homing Tsuibidan back at Piccolo and damaged Piccolo's arm. Piccolo then proceeded to tear the injured arm off to the horror of the spectators and regenerated a new one.
Piccolo had his arm stung and drained by Imperfect Cell leaving an emaciated brown stick. Piccolo managed to distract Imperfect Cell long enough to regenerate his arm back. Later on, when Imperfect Cell blasted a hole through Piccolo and threw him into the ocean, he recovered thanks to his regeneration ability.
Piccolo demonstrated that he could regenerate from any wound so long as his head was intact during the Majin Buu Saga.
Cell had the Regeneration ability because he was created partly with Piccolo's cells. On several occasions, Cell regenerated from extremely severe wounds, including one which left no part of his body except for a single cell intact, implying that his regenerative nucleus existed in each one of his cells (this was not only thanks to Regeneration, but also to Freeza's ability to survive horrifically severe wounds and still live as he was created partly with Freeza's cells).
- Note: The head was where the "regenerative nucleus", i.e. the regenerative organ, was located.
Slugg used Regeneration in Dragon Ball Z: Lord Slug. After Goku transformed into a False Super Saiyan, he damaged Slugg's arm. Slugg shocked Goku, however, when he tore it off and regenerated a new one. In the same film, Piccolo ripped off his own ears to avoid hearing Son Gohan's whistling tune (unbearable to Namekians' sensitive ears), but later used Regeneration to instantly grow his ears back to everyone's amusement.
It is unknown if Regeneration was a basic part of all Namekians since it may have took some physical and mental training before Namekians could use it consciously. It also appeared to be quite an exhausting procedure, as every time after it was performed the user breathed extremely heavily from the effort and strain and required absolute concentration of mind and body. It has been pointed out that regrowing limbs caused a severe temporary drain on the battle power of the Namekian.
Meta-Cooler had a similar ability, though it was more mechanical in nature, named the Jidō Shūfuku Nōryoku (自動 修復 能力, Jidō Shūfuku Nōryoku; Literally meaning "Auto Repair Ability") in Daizenshū 7. It should be noted that Meta-Cooler (the first encounter) is not the "real" Cooler (he is revealed to be one of many mechanical copies of the original Cooler; these "Meta-Cooler" bodies where created by the Big Gete Star), the "real" Meta-Cooler is the still living disembodied head of Cooler that had merged with the Big Gete Star, with Cooler's head becoming one with its core. Like Freeza, Cooler has the ability to survive virtually any wound (like being vivisected in half or decapitation) and function (as seen with both Freeza and Cooler).
Baby's ability to liquefy may have gave him a form-limited regenerative ability that was likely bio-mechanical in nature.
Bio-Broly had a similar ability to Regeneration. When Kuririn made a direct hit to Broly's head with a Destructo Disc, it regenerated and reattached to his body.
Future Cell was another bio-mechanical creature with Regeneration. This was because he was programmed with the cells of Piccolo.
Majin Boo's Regeneration (魔人 ブウ の 再生, Majin Bū no Saisei) allowed him to regenerate lost appendages, holes in his body, recover from being blown to pieces, or even being blasted to vapor so long as he was not completely atomized. In his case though, his entire body is in an unstable form and each singular piece of him, even as a fine dust, is able to reform back to his original shape. Majin Boo's Regeneration was not Namekian in nature since he was able to regenerate wounds long before he absorbed Piccolo.
Janemba, although not known for having great regenerative powers, was able to heal from the injury Pikkon inflicted on him by insulting him almost instantly.
- Most Namekians (Regeneration)
- Metal Coola (Nano-regeneration - Any injury Metal Cooler might suffer is instantly detected and repaired, and whatever flaws in his design that allowed the injury are corrected.)
- Majin Boo
- Super Boo
- Kid Boo
- Rage Shen Long
- Omega Shen Long (With the power of the Five-Star Ball)
- Bio Broly
- 再 (sai) = again/newly
- 生 (sei) = life/raw