forcer

Noun

 * 1) The solid piston of a force pump; the instrument by which water is forced in a pump.
 * 2) A small hand pump for sinking pits, draining cellars, etc.
 * 3) A bell-shaped lidded pot for growing rhubarb, used to limit photosynthesis by excluding light, encouraging early-season growth and blanched stems.
 * 1) A bell-shaped lidded pot for growing rhubarb, used to limit photosynthesis by excluding light, encouraging early-season growth and blanched stems.

Etymology
, from, a verb based on , a noun based on.

Verb

 * 1) to force