drain > define

Emptying something accomplished by allowing liquid to run out of it.
- synonyms: drainage
Tube inserted into a body cavity (as during surgery) to remove unwanted material.
A pipe through which liquid is carried away.
- synonyms: drainpipe, waste pipe
A gradual depletion of energy or resources.
- usage: "a drain on resources"; "a drain of young talent by emigration"

Flow off gradually.
- usage: "The rain water drains into this big vat"
- synonyms: run out
Deplete of resources.
- usage: "The exercise class drains me of energy"
Empty of liquid; drain the liquid from.
- usage: "We drained the oil tank"
Make weak.
- usage: "Life in the camp drained him"
- synonyms: enfeeble, debilitate

(v.t.) To exhaust of liquid contents by drawing them off; to make gradually dry or empty; to remove surface water, as from streets, by gutters, etc.; to deprive of moisture; hence, to exhaust; to empty of wealth, resources or the like; as, to drain a country of its specie.
(v.t.) To filter.
(n.) The grain from the mashing tub; as, brewers' drains.
(v.t.) To draw off by degrees; to cause to flow gradually out or off; hence, to cause the exhaustion of.
(v.i.) To become emptied of liquor by flowing or dropping; as, let the vessel stand and drain.
(n.) The act of draining or of drawing off; gradual and continuous outflow or withdrawal; as, the drain of specie from a country.
(n.) That means of which anything is drained; a channel; a trench; a water course; a sewer; a sink.
(v.i.) To flow gradually; as, the water of low ground drains off.

by Webster's Revised Unabridged Dictionary

DRAIN is a means, whether natural or otherwise, by which water is allowed to flow off a property.