Definition of "foul up" []

• To make a mistake, to go wrong. (verb)
• To botch; to make a mess of. (verb)

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• "Periodically I foul up the routes here, applying spells of misdirection, so as not to be pestered by casual querists; it's a good location. ""
• "A survey team couldn't foul up so badly as to miss something as long-term deadly as a hive virus."