noun.
The act or an instance of exerting, especially a strenuous effort.
The Century Dictionary and Cyclopedia
noun.
The act of exerting; the act of putting into motion or action; effort; a striving: as, an exertion of strength or power; an exertion of the limbs or of the mind.
noun.Synonyms Endeavor, attempt, trial.
the GNU version of the Collaborative International Dictionary of English
noun.
The act of exerting, or putting into motion or action; the active exercise of any power or faculty; an effort, esp. a laborious or perceptible effort.
noun.
An expenditure of physical or mental effort.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
noun.
use of physical or mental energy; hard work
Word Usage
"Hence he has found it practically the greatest economy of mental labor to work vigorously when he is disposed to do so, and to refrain from exertion, so far as possible, _when it is felt to be an exertion_. ""