tagger

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One that tags, especially the pursuer in the game of tag.
• noun Very thin sheet iron, usually plated with tin.

from The Century Dictionary.

• noun One who tags or attaches one thing to another.
• noun That which is joined or appended to anything; an appendage.
• noun The pursuer in the game of tag.
• noun A device for removing tag-locks from sheep.
• noun plural Very thin sheet-iron, either coated or not coated with tin.
• noun A sheet of tin-plate of less than the standard gage or size of the box or lot in which it is packed; a light-weight plate. In the United States such sheets are more commonly called wasters.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who, or that which, appends or joins one thing to another.
• noun That which is pointed like a tag.
• noun Sheets of tin or other plate which run below the gauge.
• noun A device for removing taglocks from sheep.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun One who tags.
• noun computing theory A component of a parser that tags words.
• noun A person who writes graffiti using his or her tag.
• noun slang The penis.
• noun computing A program that adds tags for purposes of categorization, e.g. to a music collection.
• noun That which is pointed like a tag.
• noun plural Sheets of tin or other plate which run below the gauge.
• noun A device for removing taglocks from sheep.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun someone who appends or joins one thing to another
• noun a computer program that attaches labels to the grammatical constituents of textual matter
• noun someone who assigns labels to the grammatical constituents of textual matter