operation

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

• noun The act or process of operating or functioning.
• noun The state of being operative or functional.
• noun A process or series of acts involved in a particular form of work.
• noun An instance or method of efficient, productive activity.
• noun An unethical or illegal business.
• noun Medicine A surgical procedure for remedying an injury, ailment, defect, or dysfunction.
• noun Mathematics A process or action, such as addition, substitution, transposition, or differentiation, performed in a specified sequence and in accordance with specific rules.
• noun A logical operation.
• noun Computers An action resulting from a single instruction.
• noun A military or naval action, campaign, or mission.
• noun The headquarters or center from which a military action, flights into and out of an airfield, or other activities are controlled.
• noun The division of an organization that carries out the major planning and operating functions.

from The Century Dictionary.

• noun Embryotomy by decapitation.
• noun Amputation by a circular incision down to the bone.
• noun Removal of epithelioma of the lip by a V-shaped incision.
• noun An operation for the radical cure of hernia by closing the internal ring by a pad formed of the hernial sac.
• noun Excision of a wedge-shaped piece from the tarsus in order to restore the arch in fiat-foot.
• noun An operation for theclosure of harelip.
• noun Removal of the necrosed portion of a bone, allowing the cavity to fill with blood which clots and later becomes organized.
• noun Action; working; agency; exertion of power or influence; specifically, in psychology, the exertion of any mental power, especially an active power.
• noun A specific act or activity.
• noun The course of action or series of acts by which some result is accomplished; process.
• noun In mathematics, the substitution of one quantity for another, or the act of passing from one to the other, the second quantity being definitely related to the first, either in value or in form. An operation must not be confounded with the process by which the operation is effected. Thus, there is but one operation of extracting the cube root of a number, but there are several different processes.
• noun In war, the act of carrying out preconcerted measures by regular movements: as, military or naval operations.
• noun The state of being at work; active exercise of some specific function or office; systematic action: as, the machine is in operation.
• noun Method of working; action.
• noun Power exercised in producing an effect; peculiar efficacy of action; characteristic property or virtue.
• noun Impulse; tendency to act.
• noun An operation for Dupuytren's contraction, consisting in the subcutaneous division of the contracted bands of the palmar fascia.
• noun For vaginal atresia: a method of dilatation by the use of the finger and dull instruments, rather than by cutting.
• noun The extraction of a nasal polypus by the aid of an incision made in the middle line of the soft palate.
• noun A medio-lateral operation of lithotomy, with an angular staff.
• noun See Dieffenbach's rhinoplastic operation and Indian rhinoplastic operation.
• noun For procidentia uteri: a denudation on the anterior and posterior walls of the vagina, and formation of longitudinal septum.
• noun A pure tarsometatarsal disarticulation. See Hey's operation.
• noun Subastragaloid operation.
• noun For hernia: an operation without opening the sac.
• noun An operation for staphylorrhaphy, in which liberating incisions are made on each side of the suture.
• noun Synonyms Procedure, etc. (see process), influence, effect.

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

• noun The act or process of operating; agency; the exertion of power, physical, mechanical, or moral.
• noun The method of working; mode of action.
• noun That which is operated or accomplished; an effect brought about in accordance with a definite plan.
• noun obsolete Effect produced; influence.
• noun (Math.) Something to be done; some transformation to be made upon quantities or mathematical objects, the transformation being indicated either by rules or symbols.
• noun (Surg.) Any methodical action of the hand, or of the hand with instruments, on the human body, to produce a curative or remedial effect, as in amputation, etc.
• noun See under Calculus.

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

• noun The method by which a device performs its function.
• noun The method or practice by which actions are done.
• noun A planned undertaking.