Draft
Draft turns up in 2 fields: boilers, railroad. Here is what it means to the people in each one.
Draft in boilers
The pressure difference that pulls or pushes combustion gases through the boiler and out the chimney.
Natural draft comes from hot flue gas being lighter than outside air; forced draft uses a fan to push air in; induced draft uses a fan to pull gas out; balanced draft combines both. Draft is measured in inches of water column, as a negative number where it pulls. A typical oil burner wants about minus 0.02 inches over the fire, with somewhat more pull in the breeching.
"Overfire draft is minus 0.01 and breeching is minus 0.06, the heat exchanger's half plugged with soot."
Draft in railroad
The pulling force stretching the couplers and draft gear of a train.
The state of tension throughout a train when the locomotive is pulling and the slack between the cars is fully stretched out. Engineers must carefully manage this force, especially over undulating terrain, to prevent breaking a knuckle or tearing out a drawbar. A train is said to be in draft when the pulling forces exceed the braking or rolling resistance forces.
"Keep the train in draft as you crest the hill so the rear end doesn't run in and knock you around."