Ex-haust'ion, n.

(egz-hawst'yun), n. [Fr. exhaustion.]

1. The act of drawing out or draining off; the act of emptying completely of the contents.
2. The state of being exhausted or emptied; the state of being deprived of strength or spirits.
3. (Math.) A method of demonstration much employed by ancient geometers, nearly equivalent to the modern method of limits, and involving the principle of the reductio ad absurdum: thus, the equality of two magnitudes is proved by showing that if one is supposed either greater or less than the other, there will arise a contradiction.

Math. Dict.