Etymology: Middle English draynen, from Old English drēahnian — more at dry
Date: before 12th century
1. obsolete filter
a. to draw off (liquid) gradually or completely <drained all the water out> b. to cause the gradual disappearance of <drain the region's wealth> c. to exhaust physically or emotionally <feeling drained at the end of a long workday> 3. a. to make gradually dry <drain a swamp> b. to carry away the surface water of <the river that drains the valley> c. to deplete or empty by or as if by drawing off by degrees or in increments <drained the country of its resources> d. to empty by drinking the contents of <drain a mug of beer> 4. drop 7c, sink <drained the putt> intransitive verb 1. a. to flow off gradually b. to disappear gradually ; dwindle 2. to become emptied or freed of liquid by its flowing or dropping <waiting for the tub to drain> 3. to discharge surface or surplus water Synonyms: see deplete • drainer noun II. noun Date: 1552 1. a means (as a pipe) by which usually liquid matter is drained 2. a. the act of draining b. a gradual outflow or withdrawal ; depletion 3. something that causes depletion ; burden 4. an electrode in a field-effect transistor toward which charge carriers move — compare gate, source
New Collegiate Dictionary. 2001.