Painkiller (noun)

1. A medicine used to relieve pain.
2. A substance that is used to relieve pain.

Origin:

Late 19th century: from pain + killer.

Examples:

1. The doctor prescribed a painkiller for her headache.
2. Aspirin is a common painkiller.
3. Morphine is a strong painkiller.
4. Ibuprofen is a non-steroidal anti-inflammatory painkiller.
5. Acetaminophen is a painkiller that also reduces fever.