tagger

Short definition from Wiktionary

Noun

1. 1
   One who or that which tags: The player who tries to catch others in the game of tag.
2. 2
   One who or that which tags: A person who writes graffiti using a specific mark
3. 3
   One who or that which tags: A program or algorithm that adds tags for purposes of categorization, e.g. grammatical information to words in a document, or genres to songs in a music collection.
4. 4
   A device for removing taglocks from sheep.
5. 5
   That which is pointed like a tag.
6. 6
   The penis.
7. 7
   Sheets of tin or other plate which run below the gauge.