rail (n.1)

"horizontal bar passing from one post or support to another," c. 1300, from Old French reille "bolt, bar," from Vulgar Latin *regla, from Latin regula "rule, straight piece of wood," diminutive form related to regere "to straighten, guide" (from PIE root *reg- "move in a straight line"). Used figuratively for thinness from 1872. To be off the rails in a figurative sense is from 1848, an image from the railroads. In U.S. use, "A piece of timber, cleft, hewed, or sawed, inserted in upright posts for fencing" [Webster, 1830].

rail (n.2)

"small wading bird," mid-15c., from Old French raale (13c.), related to râler "to rattle," of unknown origin, perhaps imitative of its cry.

rail (v.1)

"complain," mid-15c., from Middle French railler "to tease or joke" (15c.), perhaps from Old Provençal ralhar "scoff, to chat, to joke," from Vulgar Latin *ragulare "to bray" (source also of Italian ragghiare "to bray"), from Late Latin ragere "to roar," probably of imitative origin. See rally (v.2). Related: Railed; railing.

rail (v.2)

"fence in with rails," late 14c., from rail (n.1). Related: Railed; railing.

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Definitions of rail from WordNet
rail (v.)
complain bitterly;
Synonyms: inveigh
rail (v.)
enclose with rails;
rail in the old graves
Synonyms: rail in
rail (v.)
provide with rails;
The yard was railed
rail (v.)
separate with a railing;
rail off the crowds from the Presidential palace
Synonyms: rail off
rail (v.)
convey (goods etc.) by rails;
fresh fruit are railed from Italy to Belgium
rail (v.)
travel by rail or train;
They railed from Rome to Venice
Synonyms: train
rail (v.)
lay with rails;
hundreds of miles were railed out here
rail (v.)
fish with a handline over the rails of a boat;
They are railing for fresh fish
rail (v.)
spread negative information about;
Synonyms: vilify / revile / vituperate
rail (v.)
criticize severely;
She railed against the bad social policies
Synonyms: fulminate
rail (n.)
a barrier consisting of a horizontal bar and supports;
Synonyms: railing
rail (n.)
short for railway;
he was concerned with rail safety
he traveled by rail
rail (n.)
a bar or pair of parallel bars of rolled steel making the railway along which railroad cars or other vehicles can roll;
Synonyms: track / rails / runway
rail (n.)
a horizontal bar (usually of wood or metal);
rail (n.)
any of numerous widely distributed small wading birds of the family Rallidae having short wings and very long toes for running on soft mud;