Yes, mark is playable
...and is worth 11 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Mark" Definition
noun
A boundary between countries.
A distinctive trait or property: Good manners are the mark of a civilized person.
A lasting effect: The experience had left its mark.
verb-intransitive
Archaic To pay attention; notice.
Sports & Games To keep score.
To determine academic grades: a teacher who marks strictly.
To make a visible impression: This pen will mark under water.
To receive a visible impression: The floor marks easily.
idiom
Beside the mark Beside the point; irrelevant.
Mark time To function in an apathetic or ineffective manner.
Mark time To move the feet alternately in the rhythm of a marching step without advancing.
Mark time To suspend progress for the time being; wait in readiness.
phrasal-verb
Mark down To mark for sale at a lower price.
Mark up To deface by covering with marks.
Mark up To mark for sale at a higher price.
verb-transitive
Sports To guard (an opponent), as in soccer.
Sports & Games To record (the score) in various games.
To distinguish or characterize: the exuberance that marks her writings; marked the occasion with celebrations.
To evaluate (academic work) according to a scale of letters or numbers; grade.
To form, make, or depict by making a mark: marked a square on the board.
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