Occupation crossing
A road crossing a railway by overbridge, underpass, or level
crossing, where the railway runs through private property.
Off
A signal showing clear to proceed is said to be off.
To pull off a signal is to return it to it's all clear
indication.
Oiling Up
Topping up the various oil reservoirs around a locomotive, or other
rolling stock, before commencing work.
Old Oak Common
A main locomotive and carriage depot in London. It was built by the
Great Western Railway to service their London terminus (Paddington
Station).
On
In signaling terms, a signal at danger is said to be on.
On shed
Within the bounds of a locomotive shed.
Open Coach
Coach with the seating arranged in open saloons. Open coaches nearly
always have corridor connections. Otherwise, they are more normally
described as "saloon coaches". (C.f. compartment coach.)
Orenstein & Koppell
Locomotive builders
Outer-home signal
Where it is necessary to have two consecutive stop signals within
station limits before the platforms are reached, the first one
reached in the normal direction of travel is called the "outer-home
signal".
Outside cylinders
Steam-locomotive cylinders which are secured on the outside of the
frame.
Outside frames
Vehicle frames, the sides of which are outside the wheels.
Outside valve-gear
Steam-locomotive valve-gear which is located outside the frame.