What does "forcing" mean?

Forcing: (Gardening) The art of raising plants, flowers, and fruits at an earlier season than the natural one, as in a hitbed or by the use of artificial heat. Forcing bed or pit, a plant bed having an under layer of fermenting manure, the fermentation yielding bottom heat for forcing plants; a hotbed. -- Forcing engine, a fire engine. -- Forcing fit (Mech.), a tight fit, as of one part into a hole in another part, which makes it necessary to use considerable force in putting the two parts together. -- Forcing house, a greenhouse for the forcing of plants, fruit trees, etc. -- Forcing machine, a powerful press for putting together or separating two parts that are fitted tightly one into another, as for forcing a crank on a shaft, or for drawing off a car wheel from the axle. -- Forcing pump. See Force pump (b).