Dropper

noun

1. A utensil for dispensing a single drop of liquid at a time.
2. One who drops something, especially one who drops a specific item to cause mischief.

   "The dropper left the suitcase with the bomb next to the garbage can."

3. A software component designed to install malware on a target system.
4. A fly that drops from the leaden above the bob or end fly.
5. A branch vein which drops off from, or leaves, the main lode.