to withdraw or draw off (a liquid) gradually; remove slowly or by degrees, as by filtration

to drain oil from a crankcase.

to withdraw liquid gradually from; make empty or dry by drawing off liquid

to drain a crankcase.

to exhaust the resources of

to drain the treasury.

to deprive of strength; tire.

to flow off gradually.

to become empty or dry by the gradual flowing off of liquid or moisture

This land drains into the Mississippi.

something, as a pipe or conduit, by which a liquid drains.

Surgery . a material or appliance for maintaining the opening of a wound to permit free exit of fluids.

gradual or continuous outflow, withdrawal, or expenditure.

something that causes a large or continuous outflow, expenditure, or depletion

Medical expenses were a major drain on his bank account.

an act of draining.

Physical Geography .

an artificial watercourse, as a ditch or trench.

a natural watercourse modified to increase its flow of water. ?

go down the drain

to become worthless or profitless.

to go out of existence; disappear.