off the rails Definition

rail¹
noun

1. A bar, usually a horizontal one, supported by vertical posts, forming a fence or barrier.
2. A horizontal bar used to hang things on.

Example: a picture rail
3. Either of a pair of lengths of metal, usually steel, forming a track for the wheels of a train, tramcar or other vehicle.
4. The railway as a means of travel or transport.

Example: go by rail
5. Said of a door, wooden framework, etc: a horizontal section in panelling or framing.
6. The fence which forms the inside barrier of a racecourse.

Form: the rails
7. naut.
The capping part of bulwarks.

verb railed, railing

1. To provide with rails.
2. To enclose (eg a space) within a rail or rails.

Form: rail something in (usually)
Form: rail something off

Idiom: off the rails

Mad; eccentric.

Not functioning or behaving normally or properly.

Disorganized.

Etymology: 13c: from French reille iron rod, from Latin regula staff, rod.