Third-person singular simple present indicative form of derail. (verb)
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Use "derails" in a sentence
"Is it just a matter of time before the Duggar train derails in front of the cameras?"
"Lilian – no you’re right – it does come from Nights at the Circus, if you mean the bit where the train derails and they all wander off into the Siberian wilds and the women come across the prison … It is a wonderfully powerful passage in an amazing novel."
"Obviously, it's difficult to render colloquial reportage in a form that is both readable and faithful to the original, but too often a clunky or over-literal phrase derails the narrative."