Yes, exercise is playable
...and is worth 18 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Exercise" Definition
noun
A program that includes speeches, presentations, and other ceremonial activities performed before an audience: graduation exercises.
A task, problem, or other effort performed to develop or maintain fitness or increase skill: a piano exercise; a memory exercise.
Activity that requires physical or mental exertion, especially when performed to develop or maintain fitness: took an hour of vigorous daily exercise at a gym.
An act of employing or putting into play; use: the free exercise of intellect; the exercise of an option.
An activity having a specified aspect: an undertaking that was an exercise in futility.
verb-transitive
To absorb the attentions of, especially by worry or anxiety.
To bring to bear; exert: "The desire to be re-elected exercises a strong brake on independent courage” ( John F. Kennedy).
To carry out the functions of: exercise the role of disciplinarian.
To execute the terms of (a stock option, for example).
To put into play or operation; employ: Proceed, but exercise caution.
verb-intransitive
verb
To make effective in action .
To implement the terms of (as an option).
To use repeatedly in order to strengthen or develop .
To train (as troops) by drills and maneuvers.
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