effort

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The use of physical or mental energy to do something; exertion.
2. n. A difficult exertion of the strength or will: It was an effort to get up.
3. n. A usually earnest attempt: Make an effort to arrive promptly.
4. n. Something done or produced through exertion; an achievement: a play that was his finest effort.
5. n. Physics Force applied against inertia.

Century Dictionary and Cyclopedia

1. n. Voluntary exertion; a putting forth of the will, consciously directed toward the performance of any action, external or internal, and usually prepared by a psychological act of “gathering the strength” or coördination of the powers. A voluntary action, not requiring such preparation, is, both in the terminology of psychology and in ordinary language, said to be performed without effort.
2. n. The result of exertion; something done by voluntary exertion; specifically, a literary, oratorical, or artistic work.
3. n. In mech., a force upon a body due to a definite cause. Thus, a heavy body on an inclined plane is said to have an effort to fall vertically. Also, the effective component of a force.
4. To strengthen; reinforce.

Wiktionary

1. n. The amount of work involved in performing an activity; exertion.
2. n. An endeavour.
3. v. To make an effort.

GNU Webster's 1913

1. n. An exertion of strength or power, whether physical or mental, in performing an act or aiming at an object; more or less strenuous endeavor; struggle directed to the accomplishment of an object.
2. n. A force acting on a body in the direction of its motion.
3. v. To stimulate.

WordNet 3.0

1. n. earnest and conscientious activity intended to do or accomplish something
2. n. use of physical or mental energy; hard work
3. n. a notable achievement
4. n. a series of actions advancing a principle or tending toward a particular end