/ fɔɪl; NAmE / noun , verb
■ noun
1.
( BrE also ˌsilver ˈfoil ) [ U ] metal made into very thin sheets that is used for covering or wrapping things, especially food :
( BrE )
aluminium foil
( NAmE )
aluminum foil
—see also tinfoil
2.
[ U ] paper that is covered in very thin sheets of metal :
The chocolates are individually wrapped in gold foil.
3.
[ C ] foil (for sb/sth) a person or thing that contrasts with, and therefore emphasizes, the qualities of another person or thing :
The pale walls provide a perfect foil for the furniture.
4.
[ C ] a long thin light sword used in the sport of fencing
—picture at fencing
■ verb
[ vn ] [ often passive ] to stop sth from happening, especially sth illegal; to prevent sb from doing sth
SYN thwart :
to foil a plan / crime / plot
Customs officials foiled an attempt to smuggle the paintings out of the country.
They were foiled in their attempt to smuggle the paintings.
••
WORD ORIGIN
verb Middle English (in the sense trample down ): perhaps from Old French fouler to full cloth, trample, based on Latin fullo fuller.
noun senses 1 to 3 Middle English : via Old French from Latin folium leaf.
noun sense 4 late 16th cent.: of unknown origin.