Definition of rail noun from the Oxford Advanced Learner's Dictionary

rail

noun

reɪl

reɪl

1 [countable] a wooden or metal bar placed around something as a barrier or to provide supportShe leaned on the ship's rail and gazed out to sea. see also guard rail, handrail

2 [countable] a bar fixed to the wall for hanging things ona picture/curtain/towel rail

3 [countable, usually plural] each of the two metal bars that form the track that trains run on

4 [uncountable] (often before another noun) railways/railroads as a means of transportto travel by railrail travel/services/faresa rail link/network

Idioms

get back on the rails

(informal) to become successful again after a period of failure, or to begin functioning normally againHe has helped get the company back on the rails again.

go off the rails

(informal)1 to start behaving in a strange or unacceptable manner, for example, drinking a lot or taking drugsShe went completely off the rails after her sister died.2 to lose control and stop functioning correctlyThe company has gone badly off the rails in recent years.

more at jump the rails at jump verb