1. To run off the rails.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• defaul,
• detaill,
• detaile,
• deitail,
• dril,
• merril,
• deveil,
• denaili,
• deray,
• deail,
• verall,
• dedal,
• neral,
• detaul,
• perail,
• denail,
• domail,
• betrail,
• datail,
• deaily

• devil,
• aerial,
• peril,
• frail,
• drool,
• trail,
• drill,
• drawl,
• retail,
• rail,
• trial,
• trawl,
• drain,
• deal,
• dearly,
• detail,
• denial,
• decal,
• serial.

The adverb form of "derail" is "derailingly".

The adjective form of the word "derail" is "derailed".

The plural form of "derail" is "derails"

The singular form of the word "derail" is "derailment"