The Collaborative International Dictionary of English v.0.48:

Suck \Suck\ (s[u^]k), v. t. [imp. & p. p. Sucked (s[u^]kt); p.
   pr. & vb. n. Sucking.] [OE. suken, souken, AS. s[=u]can,
   s[=u]gan; akin to D. zuigen, G. saugen, OHG. s[=u]gan, Icel.
   s[=u]ga, sj[=u]ga, Sw. suga, Dan. suge, L. sugere. Cf.
   Honeysuckle, Soak, Succulent, Suction.]
   1. To draw, as a liquid, by the action of the mouth and
      tongue, which tends to produce a vacuum, and causes the
      liquid to rush in by atmospheric pressure; to draw, or
      apply force to, by exhausting the air.
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   2. To draw liquid from by the action of the mouth; as, to
      suck an orange; specifically, to draw milk from (the
      mother, the breast, etc.) with the mouth; as, the young of
      an animal sucks the mother, or dam; an infant sucks the
      breast.
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   3. To draw in, or imbibe, by any process resembles sucking;
      to inhale; to absorb; as, to suck in air; the roots of
      plants suck water from the ground.
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   4. To draw or drain.
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            Old ocean, sucked through the porous globe.
                                                  --Thomson.
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   5. To draw in, as a whirlpool; to swallow up.
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            As waters are by whirlpools sucked and drawn.
                                                  --Dryden.
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   To suck in, to draw into the mouth; to imbibe; to absorb.


   To suck out, to draw out with the mouth; to empty by
      suction.

   To suck up, to draw into the mouth; to draw up by suction
      or absorption.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sucking \Suck"ing\, a.
   Drawing milk from the mother or dam; hence, colloquially,
   young, inexperienced, as, a sucking infant; a sucking calf.
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         I suppose you are a young barrister, sucking lawyer, or
         that sort of thing.                      --Thackeray.
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   Sucking bottle, a feeding bottle. See under Bottle.

   Sucking fish (Zool.), the remora. See Remora. --Baird.

   Sucking pump, a suction pump. See under Suction.

   Sucking stomach (Zool.), the muscular first stomach of
      certain insects and other invertebrates which suck liquid
      food.
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WordNet (r) 3.0 (2006):

sucking
    n 1: the act of sucking [syn: sucking, suck, suction]