fa·tigue (f?-t?g?)n.1. Physical or mental weariness resulting from effort or activity.2. Something, such as tiring effort or activity, that causes tiredness or weariness: the fatigue of a long hike.3. Physiology The decreased capacity or complete inability of an organism, organ, or part to function normally because of excessive stimulation or prolonged exertion.4. The weakening or failure of a material, such as metal or wood, resulting from prolonged stress.5. a. Manual or menial labor, such as barracks cleaning, assigned to soldiers.b. fatigues Clothing worn by military personnel for labor or for field duty.v. fa·tigued, fa·tigu·ing, fa·tigues v.tr.1. To tire out; exhaust.2. To create fatigue in (a metal or other material).v.intr. To be or become tired. See Synonyms at tire1.[French, from Old French, from fatiguer, to fatigue, from Latin fat?g?re.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.fatigue (f??ti??) n1. physical or mental exhaustion due to exertion2. a tiring activity or effort3. (Physiology) physiol the temporary inability of an organ or part to respond to a stimulus because of overactivity4. (Mechanical Engineering) the progressive cracking of a material subjected to alternating stresses, esp vibrations5. the temporary inability to respond to a situation or perform a function, because of overexposure or overactivity: compassion fatigue. 6. (Military) a. any of the mainly domestic duties performed by military personnel, esp as a punishmentb. (as modifier): fatigue duties. 7. (Military) (plural) special clothing worn by military personnel to carry out such dutiesvb, -tigues, -tiguing or -tigued8. to make or become weary or exhausted9. (Mechanical Engineering) to crack or break (a material or part) by inducing fluctuating stresses in it, or (of a metal or part) to become weakened or fail as a result of fluctuating stresses[C17: from French, from fatiguer to tire, from Latin fat?g?re] fatigable adj fa?tigueless adjCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014fa?tigue (f??tig) n., adj., v. -tigued, -ti?guing. n. 1. weariness from bodily or mental exertion. 2. a cause of weariness; labor; exertion. 3. temporary diminution of the irritability or functioning of organs, tissues, or cells after excessive exertion or stimulation. 4. the weakening or breakdown of material subjected to stress, esp. a repeated series of stresses: metal fatigue. 5. Also called fatigue? du`ty. menial labor performed by military personnel. 6. fatigues. Also called fatigue? clothes`. the military clothing worn for fatigue duty or field activity. adj. 7. of or pertaining to fatigues or clothing made to resemble them. v.t. 8. to weary with bodily or mental exertion; exhaust; enervate. v.i. 9. to become fatigued. [1685?95;