noun area or district drained; as, the drainage of the po, the thames, ·etc.
2. drainage ·noun the mode in which the waters of a country pass off by its streams and rivers.
3. drainage ·noun the act, process, or means of drawing off the pus or fluids from a wound, abscess, ·etc.
4. drainage ·noun a draining; a gradual flowing off of any liquid; also, that which flows out of a drain.
5. drainage ·noun the system of drains and their operation, by which superfluous water is removed from towns, railway beds, mines, and other works.