A Barnacle

1. A marine crustacean of the subclass Cirripedia that attaches itself to submerged surfaces such as tidal rocks or the bottoms of ships.Hypernyms: arthropod, crustacean
2. The barnacle goose.
3. (engineering, slang) In electrical engineering, a change made to a product on the manufacturing floor that was not part of the original product design.
4. (computing, slang) On printed circuit boards, a change such as soldering a wire in order to connect two points, or addition such as an added resistor or capacitor, subassembly or daughterboard.
5. (software engineering, slang) A deprecated or obsolete file, image or other artifact that remains with a project even though it is no longer needed.(The addition of quotations indicative of this usage is being sought):
6. (obsolete, in the plural) An instrument like a pair of pincers, to fix on the nose of a vicious horse while shoeing so as to make it more tractable.Synonym: twitch
7. (archaic, Britain, slang, in the plural) A pair of spectacles.
8. (slang, obsolete) A good job, or snack easily obtained.
9. (slang) A worldly sailor.Synonym: shellback