1 [foil]
verb (used with object)
to prevent the success of; frustrate; balk: Loyal troops foiled his attempt to overthrow the government.
to keep (a person) from succeeding in an enterprise, plan, etc.
Archaic. a defeat; check; repulse.

1250–1300; Middle English foilen, < Anglo-French foller, Old French fuler to trample, full (cloth). See full2

foilable, adjective
unfoilable, adjective

1. thwart; impede, hamper. Unabridged


2 [foil]
metal in the form of very thin sheets: aluminum foil.
the metallic backing applied to glass to form a mirror.
a thin layer of metal placed under a gem in a closed setting to improve its color or brilliancy.
a person or thing that makes another seem better by contrast: The straight man was an able foil to the comic.
Architecture. an arc or a rounded space between cusps, as in the tracery of a window or other ornamentation.
verb (used with object)
to cover or back with foil.
to set off by contrast.

1350–1400; Middle English foille, foil < Old French fuelle, fueille, foille (< Latin folia leaves), fuel, fueil, foil (< Latin folium leaf, blade)

4. contrast, complement, counterpart.


3 [foil]
noun Fencing.
a flexible four-sided rapier having a blunt point.
foils, the art or practice of fencing with this weapon, points being made by touching the trunk of the opponent's body with the tip of the weapon.

1585–95; origin uncertain Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
foil1 (fɔɪl)
1.  to baffle or frustrate (a person, attempt, etc)
2.  hunting (of hounds, hunters, etc) to obliterate the scent left by a hunted animal or (of a hunted animal) to run back over its own trail
3.  archaic to repulse or defeat (an attack or assailant)
4.  hunting any scent that obscures the trail left by a hunted animal
5.  archaic a setback or defeat
[C13 foilen to trample, from Old French fouler, from Old French fuler tread down, full²]

foil2 (fɔɪl)
1.  metal in the form of very thin sheets: gold foil; tin foil
2.  the thin metallic sheet forming the backing of a mirror
3.  a thin leaf of shiny metal set under a gemstone to add brightness or colour
4.  a person or thing that gives contrast to another
5.  architect a small arc between cusps, esp as used in Gothic window tracery
6.  aerofoil short for hydrofoil
7.  to back or cover with foil
8.  architect Also: foliate to ornament (windows) with foils
[C14: from Old French foille, from Latin folia leaves, plural of folium]

foil3 (fɔɪl)
a light slender flexible sword tipped by a button and usually having a bell-shaped guard
[C16: of unknown origin]

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Word Origin & History

c.1300, foilen "to spoil a trace or scent by running over it," from O.Fr. fouler "trample," from V.L. *fullare "to clean cloth" (by treading on it), from L. fullo "one who cleans cloth, fuller," of unknown origin. Sense of "frustrate the efforts of" first recorded 1660s. Related: Foiled; foiling. Foiled
again! as a cry of defeat and dismay is from at least 1847.

"thin sheet of metal," late 14c., from O.Fr. fueille "leaf," from L. folia "leaves," pl. (mistaken for fem. sing.) of folium "leaf" (see folio). The sense of "one who enhances another by contrast" (1580s) is from the practice of backing a gem with metal foil to make it shine
better. The meaning "light sword used in fencing" (1590s) could be from this sense, or from foil (v.). The modern sense of "metallic food wrap" is from 1946.
Online Etymology Dictionary, © 2010 Douglas Harper
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Computing Dictionary

FOIL definition

File Oriented Interpretive Language. CAI language.
["FOIL - A File Oriented Interpretive Language", J.C. Hesselbart, Proc ACM 23rd National Conf (1968)].

The Free On-line Dictionary of Computing, © Denis Howe 2010
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Encyclopedia Britannica


in architecture, leaf-shaped, indented spaces which, combined with cusps (small, projecting arcs outlining the leaf design), are found especially in the tracery (decorative openwork) of Gothic windows. The term is derived from the Latin folium, meaning "leaf." A window or wall ornamented with foils is referred to as foiled. There are three kinds of such stylized foliated decoration: trefoil, quatrefoil, and cinquefoil, or three-, four-, and five-lobed leaves.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Use the minimum amount of tin foil and plastic wrap to get the job done.
Place the baking pan onto tin foil and place into the oven.
The creamy, understated bean purée is a great foil for the intense flavor of
  grilled sardines.
Make a similar ramp using a plank covered with sandpaper, oil or aluminum foil.
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