From The Collaborative International Dictionary of English v.0.48:
Operation \Op`er*a"tion\, n. [L. operatio: cf. F. op['e]ration.]
1. The act or process of operating; agency; the exertion of
power, physical, mechanical, or moral.
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The pain and sickness caused by manna are the
effects of its operation on the stomach. --Locke.
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Speculative painting, without the assistance of
manual operation, can never attain to perfection.
--Dryden.
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2. The method of working; mode of action.
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3. That which is operated or accomplished; an effect brought
about in accordance with a definite plan; as, military or
naval operations.
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4. Effect produced; influence. [Obs.]
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The bards . . . had great operation on the vulgar.
--Fuller.
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5. (Math.) Something to be done; some transformation to be
made upon quantities or mathematical objects, the
transformation being indicated either by rules or symbols.
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6. (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.
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Calculus of operations. See under Calculus.
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