| 1. | to prevent the success of; frustrate; balk: Loyal troops foiled his attempt to overthrow the government. |
| 2. | to keep (a person) from succeeding in an enterprise, plan, etc. |
| 3. | Archaic. a defeat; check; repulse. |
| 1. | metal in the form of very thin sheets: aluminum foil. |
| 2. | the metallic backing applied to glass to form a mirror. |
| 3. | a thin layer of metal placed under a gem in a closed setting to improve its color or brilliancy. |
| 4. | a person or thing that makes another seem better by contrast: The straight man was an able foil to the comic. |
| 5. | Architecture. an arc or a rounded space between cusps, as in the tracery of a window or other ornamentation. |
| 6. | an airfoil or hydrofoil. |
| 7. | to cover or back with foil. |
| 8. | to set off by contrast. |

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