fly in the face of, to

fly in the face of someone or something

 and fly in the teeth of someone or something
Fig. to challenge someone or something; to go against someone or something. This idea flies in the face of everything we know about matter and energy. You had better not fly in the face of the committee.
See also: face, fly, of

fly in the face of

Also, fly in the teeth of. Act in direct opposition to or defiance of. For example, This decision flies in the face of all precedent, or They went out without permission, flying in the teeth of house rules. This metaphoric expression alludes to a physical attack. [Mid-1500s]
See also: face, fly, of

fly in the face of

be openly at variance with what is usual or expected.
See also: face, fly, of

fly in the face of, to

To challenge, to take on despite overwhelming odds. This expression, which often adds something that one flies in the face of—danger, Providence, or the like—may well come from the barnyard, alluding to an angry hen flying in the face of another, larger animal, or to falconry, where an irritated hawk might fly into its master’s face. It appeared in print in the sixteenth century and was well on its way to being a cliché by the time Henry Fielding wrote, “This was flying in Mr. Alworthy’s face” (Tom Jones, 1749).
See also: face, fly