intr. & tr.v. de·railed, de·rail·ing, de·rails 1. To run or cause to run off the rails. 2. To come or bring to a sudden halt: a campaign derailed by lack of funds; a policy that derailed under the new administration. [French dérailler : dé-, off (from Old French de-; see DE-) + rail, rail (from English; see RAIL1).] de·railment n. |
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