marker

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

• noun One that marks or serves as a mark, as.
• noun A bookmark.
• noun A tombstone.
• noun A milestone.
• noun An implement, especially a felt-tipped pen, used for marking or writing.
• noun One who marks objects, especially for industrial purposes.
• noun One who grades student papers.
• noun A device, such as a line, stake, or flag, set on a playing field and showing the playing or scoring position.
• noun A player who guards an opponent, as in soccer.
• noun An official in certain court games, such as squash, who mainly judges whether the ball is out of play and whether a fault or let has occurred.
• noun One that keeps score in various games.
• noun A score in a game.
• noun Slang A written, signed promissory note.
• noun A chemical or physical characteristic that indicates the presence of something, especially.
• noun A genetic marker.
• noun A biomarker.
• noun Linguistics An element that indicates grammatical or semantic class or function, such as an inflectional affix.

from The Century Dictionary.

• noun One who or that which marks.
• noun A counter used in card-playing.
• noun One who marks or notices; a close observer; hence, rarely, a marksman.
• noun In agriculture, some implement used for tracing lines on the ground, as the position to be occupied by a row of plants or hills, or the like.
• noun In a sewing-machine, an attachment for making upon the cloth, as it passes the needle, a slight crease that may serve as a guide for folding a tuck, or for another line of stitching; a tuck-creaser.
• noun A pen or stylus used for marking or recording.
• noun Specifically, a counter (an oblong piece of bone) used in faro.
• noun At poker, any object placed upon the table to show that a player who has no chips is still in the pool: sometimes used in table-stakes to indicate that the player is supposed to have as much money in front of him as any other person at the table.
• noun In railroading, a flag, lamp, or other signal placed upon an engine or train, or upon an electric car, to indicate its character, destination, etc. The green flag at the end of a train is a marker, as is also a red tail-light, or an extra light upon a locomotive.

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

• noun One who keeps account of a game played, as of billiards.
• noun A counter used in card playing and other games.
• noun (Mil.) The soldier who forms the pilot of a wheeling column, or marks the direction of an alignment.
• noun An attachment to a sewing machine for marking a line on the fabric by creasing it.

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

• noun An object used to mark a location.
• noun Someone or something that marks.
• noun A felt-tipped pen.
• noun slang A signed note of a debt to be paid.
• noun slang, figuratively A nonmonetary debt owed to someone, especially in return for a favor.
• noun paintball A device that fires a paintball
• noun sports A defending player who stays close to an opponent in order to mark them.
• verb To mark or write on (something) using a marker

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

• noun a writing implement for making a mark
• noun some conspicuous object used to distinguish or mark something
• noun a distinguishing symbol