RAILROAD TERMS AND SLANG - All Aboard: The Complete North American Train Travel Guide - page 325

dynamic braking: This is another kind of braking, which uses the
locomotive's traction motors to produce rather than consume
electricity. If the locomotive is a pure electric, this power is fed
back into the system through the overhead wire; if it's a diesel-
electric, it's converted to heat and blown out through the vents in
the top of the locomotive. Either way, the process slows the loco-
motive. Dynamic braking will only slow a train gradually and
therefore is used in much the same way a driver downshifts a car
to control the speed when heading down a hill. See also air brake .
electric locomotive: Any locomotive that is powered by electricity and
gets that power directly from an outside source—that is, from an
overhead wire (the catenary ) or from an electrified third rail.
engine: Technically, this refers to the machinery that produces
energy. But in the context of this topic, engine is frequently used
as a synonym for locomotive .
engineer: The person who actually gets paid for sitting in the cab
of a locomotive and driving it—something many of us would do
for free. (In Europe and elsewhere around the world, this person
is called the driver.)
equipment (also called rolling stock): Engines and railcars of all kinds—
that is, anything that rolls along the tracks.
express train: A passenger train that operates with minimum
delays, usually meaning it makes only a few stops—or none at
all—between its point of origin and its ultimate destination. An
express freight operates in the same fashion.
extra train: Any train that does not appear on the published time-
table. The airline equivalent is called an extra section .