out of bounds

out of bounds idiom
Beyond established limits, breaking the rules, unreasonable. For example, Calling the teacher a liar—that's out of bounds. This expression alludes to the boundaries of the playing area in numerous sports and to the rules applying to them. Its figurative use dates from the 1940s. [Early 1800s] Also see within bounds.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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