noun
restorative medicine; analeptic
Medical term for a medicine that restores strength or consciousness; also used in fantasy/game contexts for a potion that recovers health or stamina.
この回復薬を飲めば、すぐに体力が戻ります。
If you drink this restorative medicine, your strength will return quickly.
ゲームの中で、回復薬を使ってHPを回復した。
In the game, I used a recovery potion to restore my HP.
薬 is a broad term for medicine or drug; 回復薬 narrows it to a restorative type.
Compound of 回復 (recovery) + 薬 (medicine). The exact historical derivation is uncertain, but the word follows a common pattern for naming medicinal products.