Foil (fluid mechanics) definition

(1) A light slender flexible sword tipped by a button

(2) A piece of thin and flexible sheet metal

"The photographic film was wrapped in foil"

(3) Picture consisting of a positive photograph or drawing on a transparent base; viewed with a projector

(4) 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

"The fins of a fish act as hydrofoils"

(5) Anything that serves by contrast to call attention to another thing's good qualities

"Pretty girls like plain friends as foils"

(6) Cover or back with foil

"Foil mirrors"

(7) Hinder or prevent (the efforts, plans, or desires) of

"What ultimately frustrated every challenger was Ruth's amazing September surge"

"Foil your opponent"

(8) Enhance by contrast

"In this picture, the figures are foiled against the background"