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.
   [1913 Webster]

         I suppose you are a young barrister, sucking lawyer, or
         that sort of thing.                      --Thackeray.
   [1913 Webster]

   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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sucking fish
    n 1: marine fishes with a flattened elongated body and a sucking
         disk on the head for attaching to large fish or moving
         objects [syn: remora, suckerfish, sucking fish]