Source : Webster's Revised Unabridged Dictionary (1913)

Exhaust \Ex*haust"\, v. t. [imp. & p. p. {Exhausted}; p. pr. &
   vb. n. {Exhausting}.] [L. exhaustus, p. p. of exhaurire; ex
   out + haurire, haustum, to draw, esp. water; perhaps akin to
   Icel. asua to sprinkle, pump.]
   1. To draw or let out wholly; to drain off completely; as, to
      exhaust the water of a well; the moisture of the earth is
      exhausted by evaporation.

   2. To empty by drawing or letting out the contents; as, to
      exhaust a well, or a treasury.

   3. To drain, metaphorically; to use or expend wholly, or till
      the supply comes to an end; to deprive wholly of strength;
      to use up; to weary or tire out; to wear out; as, to
      exhaust one's strength, patience, or resources.

            A decrepit, exhausted old man at fifty-five.
                                                  --Motley.

   4. To bring out or develop completely; to discuss thoroughly;
      as, to exhaust a subject.

   5. (Chem.) To subject to the action of various solvents in
      order to remove all soluble substances or extractives; as,
      to exhaust a drug successively with water, alcohol, and
      ether.

   {Exhausted receiver}. (Physics) See under {Receiver}.

   Syn: To spend; consume; tire out; weary.

Exhausting \Ex*haust"ing\, a.
   Producing exhaustion; as, exhausting labors. --
   {Ex*haust"ing}, adv.

Exhausting \Ex*haust"ing\, a.
   Producing exhaustion; as, exhausting labors. --
   {Ex*haust"ing}, adv.

Source : WordNet®

exhausting
     adj 1: having a debilitating effect; "an exhausting job in the hot
            sun" [syn: {draining}]
     2: producing exhaustion; "an exhausting march"; "the visit was
        especially wearing" [syn: {tiring}, {wearing}, {wearying}]