1rail 
/ˈreɪl/ noun
plural rails /ˈreɪl/ noun 1 [count] a : a bar that goes from one post or support to another and that is used to form a barrier
▪ She leaned over the rail of the ship. ▪ We sat on the fence rail and watched the cows. — see picture at house; see also guardrail, handrail
b : a bar used to hang something from
▪ He hung the curtains on the rail. 2 a [count] : one of the bars of steel that form a train's track — usually plural ▪ The train went off the rails. = (chiefly Brit) The train jumped the rails. — see also third rail
b [noncount] : 1railroad
▪ transportation by rail ▪ commuter rail [=part of a railroad made especially for people who work in a city but live outside it] — often used before another noun ▪ rail travel ▪ passenger rail service [=trains that take passengers rather than cargo] between the two cities — see also monorail
▪ She leaned over the rail of the ship. ▪ We sat on the fence rail and watched the cows. — see picture at house; see also guardrail, handrail
b : a bar used to hang something from
▪ He hung the curtains on the rail.
b [noncount] : 1railroad
▪ transportation by rail ▪ commuter rail [=part of a railroad made especially for people who work in a city but live outside it] — often used before another noun ▪ rail travel ▪ passenger rail service [=trains that take passengers rather than cargo] between the two cities — see also monorail
go off the rails
informal : to lose control and start to behave in a way that is not normal or acceptable
▪ He was a promising student but he went off the rails after he started taking drugs. ▪ The government has gone (completely) off the rails.
▪ He was a promising student but he went off the rails after he started taking drugs. ▪ The government has gone (completely) off the rails.
