From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Energy Absorption (エネルギー 吸収, Enerugii Kyūshū) is a supportive technique.
Dragon Ball Z
Energy Absorption was introduced during the Androids Saga by Artificial Human No. 19 and Doctor Gero. Due to them having mechanical components, Doctor Gero (No. 20) invented a way for him and No. 19 to absorb energy from an outside source in order to power up their own energy reserves. This was accomplished through the use of a mechanism on each hand that absorbed a Ki Blast or drained energy from a person when they were captured. Unlike the fully organic characters in the series, however, Energy Absorption was the only way for them to power up their reserves of energy when they were away from Doctor Gero's Lab. This ability later reappeared in Dragon Ball GT during the Super 17 Saga when it was used by Super Artificial Human No. 17.
Dragon Ball GT
Super 17 gained a more advanced version of this ability. The advantages allowed him to absorb energy directly into his body and use it to increase his strength, speed, and other abilities. A display of this was shown when he absorbed Son Goku's 10x Kamehameha. After he absorbed the attack, he became incredibly stronger than Goku, even in his Super Saiyan 4 form. The ability worked by creating a personal barrier around his body, causing him to absorb any form of energy that came in contact with him. The disadvantage prevented him from moving when he was absorbing energy. This ultimately led to his demise.
Cardinal Mutchy Mutchy absorbed energy by lassoing his magical whip around an opponent and the whip would than absorb their energy and transfer it to him.
Medamatcha unleashed Medas (small, mute leech-like versions of himself) and they leapt upon a person and drained them of their energy before reattaching to Medamatcha and giving him their energy. He could also jump on the person and drain the energy himself by piercing their skin with his large fangs. Medamatcha successfully used this attack on Son Gohan and then tried to use the same move on Goku, but failed when Goku proved too strong to be restrained by both him and his Medas even with their combined effort.
In the Budokai video game series, the absorption technique is commonly used by No. 19 and No. 20. In the Budokai Tenkaichi video game series, absorption allows the Artificial Humans to absorb an enemy Ki Blast and some energy-based Blast 1 and Blast 2 attacks. The energy of the attack is then added to the player's own Ki reserves for their own use. However, these select characters cannot power up on their own, relying on absorption as a means to gather energy. In Dragon Ball: Raging Blast, the energy absorption is relatively the same as in the Budokai Tenkaichi video game series, only the amount of energy absorbed is drastically reduced and it takes energy to use Energy Absorption (since it is a signature skill).
It is named in Pawā Dorein (パワー ドレイン, Pawā Dorein; Literally meaning "Power Drain") in Dragon Ball Heroes.
In the Budokai Tenkaichi video game series, Super No. 17, No. 19, and No. 20 drain their opponents' life energy and add that energy to their own, but they are supposed to get stronger and faster with each absorption and recover health like in the anime and manga. Energy Absorption was used in Dragon Ball Z: Lord Slug and Dragon Ball GT, and was also used by two non-Artificial Humans with the style being much different.