American Heritage Dictionary Entry: foil HOW TO USE THE DICTIONARY To look up an entry in The American Heritage Dictionary of the English Language, use the search window above. For best results, after typing in the word, click on the “Search” button instead of using the “enter” key. Some compound words (like bus rapid transit, dog whistle, or identity theft) don’t appear on the drop-down list when you type them in the search bar. For best results with compound words, place a quotation mark before the compound word in the search window. guide to the dictionary THE USAGE PANEL The Usage Panel is a group of nearly 200 prominent scholars, creative writers, journalists, diplomats, and others in occupations requiring mastery of language. Annual surveys have gauged the acceptability of particular usages and grammatical constructions. The Panelists NEED HELP SOLVING A CROSSWORD PUZZLE? Go to our Crossword Puzzle Solver and type in the letters that you know, and the Solver will produce a list of possible solutions. -- AMERICAN HERITAGE DICTIONARY APP The new American Heritage Dictionary app is now available for iOS and Android. THE AMERICAN HERITAGE DICTIONARY BLOG The articles in our blog examine new words, revised definitions, interesting images from the fifth edition, discussions of usage, and more. OPEN DICTIONARY PROJECT Share your ideas for new words and new meanings of old words! Start Sharing Now! -- See word lists from the best-selling 100 Words Series! Find out more! INTERESTED IN DICTIONARIES? Check out the Dictionary Society of North America at http://www.dictionarysociety.com foil 1 (foil) Share: Tweet tr.v. foiled, foil·ing, foils 1. To prevent from being successful; thwart: The alarm system foiled the thieves' robbery attempt. 2. To obscure or confuse (a trail or scent) so as to evade pursuers. n. Archaic 1. A repulse; a setback. 2. The trail or scent of an animal. [Middle English foilen, to trample, defile, variant of filen, to defile; see FILE3.] The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved. foil 2 (foil) Share: Tweet n. 1. Metal that has been formed into a thin, flexible sheet: aluminum foil. 2. A thin layer of polished metal placed under a displayed gem to lend it brilliance. 3. One that stands in contrast to and emphasizes the distinctive characteristics of another: "I am resolved my husband shall not be a rival, but a foil to me" (Charlotte Brontë). 4. The reflective metal coating on the back of a glass mirror. 5. Architecture A curvilinear, often lobelike figure or space formed between the cusps of intersecting arcs, found especially in Gothic tracery and Moorish ornament. 6. a. An airfoil. b. Nautical A hydrofoil. tr.v. foiled, foil·ing, foils 1. To cover or back with foil. 2. To wrap (strands of hair) in pieces of foil in order to isolate them after bleach or color has been applied. 3. To set off by contrast. [Middle English, from Old French foille, from Latin folia, pl. of folium, leaf; see bhel-3 in the Appendix of Indo-European roots.] The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved. foil 3 (foil) Share: Tweet n. 1. A fencing sword having a usually circular guard and a thin, flexible four-sided blade with a button on the tip to prevent injury. 2. often foils The art or sport of fencing with such a sword: a contest at foils. [Origin unknown.] The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved. Indo-European & Semitic Roots Appendices Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices: Indo-European Roots Semitic Roots The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots. 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