foil

American Heritage® Dictionary of the English Language, Fourth Edition

1. v. To prevent from being successful; thwart.
2. v. To obscure or confuse (a trail or scent) so as to evade pursuers.
3. n. Archaic A repulse; a setback.
4. n. Archaic The trail or scent of an animal.
5. n. A thin, flexible leaf or sheet of metal: aluminum foil.
6. n. A thin layer of polished metal placed under a displayed gem to lend it brilliance.
7. n. One that by contrast underscores or enhances the distinctive characteristics of another: "I am resolved my husband shall not be a rival, but a foil to me” ( Charlotte Brontë).
8. n. The reflective metal coating on the back of a glass mirror.
9. n. Architecture A curvilinear, often lobelike figure or space formed between the cusps of intersecting arcs, found especially in Gothic tracery and Moorish ornament.
10. n. An airfoil.
11. n. Nautical A hydrofoil.
12. v. To cover or back with foil.
13. v. To set off by contrast.
14. n. A fencing sword having a usually circular guard and a thin, flexible four-sided blade with a button on the tip to prevent injury.
15. n. The art or sport of fencing with such a sword. Often used in the plural: a contest at foils.

Century Dictionary and Cyclopedia

1. n. A leaf, as of a plant.
2. n. A metallic substance formed into very thin sheets by rolling and hammering: as, gold, tin, or lead foil. Gold foil is beaten out to the utmost tenuity. Tin foil has a slight alloy of copper, lead, etc. Dutch foil is made by rolling a plate of copper coated with silver into thin sheets, polishing the silver surface, varnishing it, and then laying on a coat of transparent color mixed with isinglass. A variegated Japanese foil is made by combining thin sheets of different metals in a single plate, which is so treated that the different metals or alloys show in the completed sheet like the lines or figures on a Damascus blade. These sheets are extremely flexible, and can be stamped, engraved, etc., for decorative use.
3. n. In jewelry, a thin leaf of metal placed under a precious stone to change its color, or to give it more color in case of its being inferior in that respect, or to give it additional luster by the reflection of light from the surface of the metal. Much old jewelry is made with thin and poor stones, to which effect is given by this means.
4. n. Leaf-metal placed behind translucent enamel for the same purpose as that used for precious stones. (See def. 3.) In this sense often called paillon (which see). Hence Anything of a different color or of different qualities which serves to adorn or set off another thing to advantage; that which, by comparison or contrast, sets off or shows more conspicuously the superiority of something else.
5. n. An amalgam of tin with quicksilver laid on one side of a sheet of glass to produce a reflecting surface in making a mirror.
6. n. In medieval architecture, a small arc in the tracery of a window, panel, etc., which is said to be trefoiled, quatrefoiled, cinquefoiled, multifoiled, etc., according to the number of arcs which it contains.
7. To trample upon; tread under foot.
8. To blunt; dull; deaden: as, to foil the scent in a chase.
9. To frustrate; baffle; mislead; render vain or nugatory, as an effort or attempt; thwart; balk: as, the enemy was foiled in his attempt to pass the river.
10. This your courtesy
11. Synonyms Thwart, Baffle, etc. See frustrate.
12. n. The track or trail of game when pursued.
13. n. Defeat; frustration; failure when on the point of achievement.
14. n. In wrestling, a partial fall; a fall not complete according to the rules.
15. n. A bated or blunted sword used in fencing-practice and friendly contests; now, usually, an implement used in fencing-schools, for small-sword practice only. It has a blade of small quadrangular section, a button on the point, and for the guard two open lunettes or loops, which it is common to reinforce by “shells” of thick leather. The French fencing-masters and amateurs distinguish between the fleuret or light foil and the épée d'escrime, which is like the dueling-sword or épée de combat, except in having a buttoned point, and is therefore much heavier than the fleuret. See fleuret.
16. To defile: same as file, foul.
17. In hunting, of an animal, to retrace its own track for the purpose of baffling the hounds; ‘run the foil.’ See foil, n.

Wiktionary

1. v. To prevent (something) from being accomplished.
2. v. To prevent (someone) from accomplishing something.
3. v. mathematics To multiply two binomials together.
4. n. hunting The track of an animal.
5. n. A very thin sheet of metal.
6. n. uncountable Thin aluminium/aluminum (or, formerly, tin) used for wrapping food.
7. n. A thin layer of metal put between a jewel and its setting to make it seem more brilliant.
8. n. figuratively In literature, theatre/theater, etc, a character who helps emphasize the traits of the main character.
9. n. figuratively Anything that acts to emphasise the characteristics of something.
10. n. fencing A very thin sword with a blunted (or foiled) tip
11. n. A thin, transparent plastic material on which marks are made and projected for the purposes of presentation. See transparency.
12. n. heraldry A stylized flower or leaf.
13. n. Shortened form of hydrofoil.
14. n. Shortened form of aerofoil/airfoil.

GNU Webster's 1913

1. v. To tread under foot; to trample.
2. v. To render (an effort or attempt) vain or nugatory; to baffle; to outwit; to balk; to frustrate; to defeat.
3. v. To blunt; to dull; to spoil.
4. v. obsolete To defile; to soil.
5. n. Failure of success when on the point of attainment; defeat; frustration; miscarriage.
6. n. A blunt weapon used in fencing, resembling a smallsword in the main, but usually lighter and having a button at the point.
7. n. The track or trail of an animal.
8. n. A leaf or very thin sheet of metal
9. n. (Jewelry) A thin leaf of sheet copper silvered and burnished, and afterwards coated with transparent colors mixed with isinglass; -- employed by jewelers to give color or brilliancy to pastes and inferior stones.
10. n. Anything that serves by contrast of color or quality to adorn or set off another thing to advantage.
11. n. A thin coat of tin, with quicksilver, laid on the back of a looking-glass, to cause reflection.
12. n. (Arch.) The space between the cusps in Gothic architecture; a rounded or leaflike ornament, in windows, niches, etc. A group of foils is called trefoil, quatrefoil, quinquefoil, etc., according to the number of arcs of which it is composed.

WordNet 3.0

1. v. enhance by contrast
2. v. hinder or prevent (the efforts, plans, or desires) of
3. n. a device consisting of a flat or curved piece (as a metal plate) so that its surface reacts to the water it is passing through
4. n. anything that serves by contrast to call attention to another thing's good qualities
5. n. a piece of thin and flexible sheet metal
6. n. a light slender flexible sword tipped by a button
7. v. cover or back with foil
8. n. picture consisting of a positive photograph or drawing on a transparent base; viewed with a projector