The Collaborative International Dictionary of English v.0.48:

Sink \Sink\ (s[i^][ng]k), v. i. [imp. Sunk (s[u^][ng]k), or
   (Sank (s[a^][ng]k)); p. p. Sunk (obs. Sunken, -- now
   used as adj.); p. pr. & vb. n. Sinking.] [OE. sinken, AS.
   sincan; akin to D. zinken, OS. sincan, G. sinken, Icel.
   s["o]kkva, Dan. synke, Sw. sjunka, Goth. siggan, and probably
   to E. silt. Cf. Silt.]
   1. To fall by, or as by, the force of gravity; to descend
      lower and lower; to decline gradually; to subside; as, a
      stone sinks in water; waves rise and sink; the sun sinks
      in the west.
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            I sink in deep mire.                  --Ps. lxix. 2.
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   2. To enter deeply; to fall or retire beneath or below the
      surface; to penetrate.
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            The stone sunk into his forehead.     --1 San. xvii.
                                                  49.
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   3. Hence, to enter so as to make an abiding impression; to
      enter completely.
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            Let these sayings sink down into your ears. --Luke
                                                  ix. 44.
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   4. To be overwhelmed or depressed; to fall slowly, as so the
      ground, from weakness or from an overburden; to fail in
      strength; to decline; to decay; to decrease.
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            I think our country sinks beneath the yoke. --Shak.
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            He sunk down in his chariot.          --2 Kings ix.
                                                  24.
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            Let not the fire sink or slacken.     --Mortimer.
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   5. To decrease in volume, as a river; to subside; to become
      diminished in volume or in apparent height.
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            The Alps and Pyreneans sink before him. --Addison.
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   Syn: To fall; subside; drop; droop; lower; decline; decay;
        decrease; lessen.
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The Collaborative International Dictionary of English v.0.48:

Sunk \Sunk\,
   imp. & p. p. of Sink.
   [1913 Webster]

   Sunk fence, a ditch with a retaining wall, used to divide
      lands without defacing a landscape; a ha-ha.
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WordNet (r) 3.0 (2006):

sunk
    adj 1: doomed to extinction [syn: done for(p), ruined,
           sunk, undone, washed-up]

Moby Thesaurus II by Grady Ward, 1.0:

68 Moby Thesaurus words for "sunk":
   balled up, blue, boat-shaped, boatlike, bollixed up, bowl-shaped,
   bowllike, buggered, buggered up, cast down, cavelike, cavernous,
   concave, concaved, cooked, craterlike, crestfallen, cup-shaped,
   cupped, cymbiform, debased, dejected, depressed, dish-shaped,
   dished, dishing, dishlike, down-in-the-mouth, downcast,
   downhearted, downthrown, droopy, fallen, fouled up,
   funnel-breasted, funnel-chested, funnel-shaped, gummed up,
   hashed up, hollow, hollowed, incurved, incurving, incurvous,
   infundibular, infundibuliform, loused up, low, lowered, messed up,
   mucked up, navicular, naviform, prostrate, queered, reduced,
   retiring, retreating, saucer-shaped, scaphoid, screwed up,
   scyphate, shot, snafued, snarled up, spoonlike, submerged,
   sunken