Gives the driver advance warning that the stop signal ahead may be displaying 'danger'. The distant signal is installed roughly at full braking distance on approach to the stop signal to which it applies, taking into account the gradient, the permitted speed, and the braking performance of trains. On sighting a 'caution' aspect, the driver must prepare to stop at the signal ahead.

reference:
https://en.wikipedia.org/wiki/Application_of_railway_signals#Distant_signal [accessed 24Sep2019]

A diviner, soothsayer, augur; a prophet, seer. (OED)

A diviner, soothsayer, augur; a prophet, seer. [OED]

Dobbin: An ordinary draught or farm horse [OED

An activity, undertaking, scheme. [OED]

A clever or adroit expedient or contrivance. Trickery.

Dog Days: The hottest part of the summer,[OED]

a fair held in Dublin until the late 1850s - slang term for a brawl or riot

A dance step. The OED cites a source saying " The hornpipe step, familiarly known as the double-shuffle." 

In British practice, railway directions are usually described as "up" and "down", with "up" being towards a major location. On most of the network, "up" is the direction towards London.

Reference
https://en.wikipedia.org/wiki/Rail_directions (accessed 25May21)

Dragsman: One who drives a drag. A drag is kind of vehicle; the application has varied, and it is often not distinguished from a brake or break; but in strict English use, applied to a private vehicle of the type of a stage coach, usually drawn by four horses, with seats inside and on the top. [OED]

A man who drives a dray; a low cart without sides used for carrying heavy loads: esp. that used by brewers [OED] 

Dredger: A vessel designed to remove silt etc from the bottom of a river or harbour [CPB]

A person who prepares, treats, or finishes something; spec. one employed to prepare a material or product for further processing.[OED]

A stuffed pad or wire frame worn below the waist under a woman's skirt to distend it; a bustle [OED]

Driver one who drives horses underground. Usually a boy or young man.

Reference:
Mining Occupations, Durham Mining Museum website http://www.dmm.org.uk/educate/mineocc.htm

Meaning uncertain: A driver is a piece of wood which drives the shuttle through the shed of the loom [OED]

Piers with a mechanism for tipping coal from wagons into a waiting ship. See illustration below

Swollen as with dropsy; A morbid condition characterized by the accumulation of watery fluid in the serous cavities or the connective tissue of the body [OED]