1. medicine; pharmaceuticals; (legal) drugs; pill; ointment; salve
お薬を飲みましょう。Let's take some medicine.
2. efficacious chemical (gunpowder, pesticide, etc.)
3. (pottery) glaze
4. (illegal) drug; narcotic
esp. クスリ
薬やってた経験があるってこと！？You mean you have done drugs before!?
5. small bribe