endeavor

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

• noun A conscientious or concerted effort toward an end; an earnest attempt.
• noun Purposeful or industrious activity; enterprise.
• intransitive verb To attempt (fulfillment of a responsibility or an obligation, for example) by employment or expenditure of effort.
• intransitive verb To work with a set or specified goal or purpose.

from The Century Dictionary.

• To put, apply, or exert (one's self) to do a thing: used reflexively.
• To attempt to gain; try to effect; strive to achieve or attain; strive after.
• To labor or exert one's self to do or effect something; strive; try; make an effort: followed by an infinitive.
• To direct one's efforts or labor toward some object or end; fix one's course; aim: with at, for, or after.
• Synonyms Undertake, Endeavor, etc. (see attempt); to seek, aim, struggle.
• noun An effort; an essay; an attempt; an exertion of physical or mental powers toward the attainment of an object.
• noun Synonyms Struggle, trial.

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

• intransitive verb To exert one's self; to work for a certain end.
• transitive verb To exert physical or intellectual strength for the attainment of; to use efforts to effect; to strive to achieve or reach; to try; to attempt.
• transitive verb [Obs.] to exert one's self strenuously to the fulfillment of a duty.
• noun An exertion of physical or intellectual strength toward the attainment of an object; a systematic or continuous attempt; an effort; a trial.
• noun to do one's duty; to put forth strenuous efforts to attain an object; -- a phrase derived from the Middle English phrase “to do one's dever” (duty).

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

• noun A sincere attempt. A determined or assiduous effort towards a specific goal.
• noun Enterprise; assiduous or persistent activity.
• verb To attempt through application of effort.
• verb To work with purpose.

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

• verb attempt by employing effort
• noun a purposeful or industrious undertaking (especially one that requires effort or boldness)
• noun earnest and conscientious activity intended to do or accomplish something