D defs.my
Entry 1 sense Webster, 1913

Derailment

/dĭr-āl'-mənt/ · De·rail·ment · IPA /dɪrˈeɪlmənt/
01 n. The act of going off, or the state of being off, the rails of a railroad.
  1. 1.
    The act of going off, or the state of being off, the rails of a railroad.