The Collaborative International Dictionary of English v.0.48:

Balk \Balk\ (b[add]k), n. [AS. balca beam, ridge; akin to Icel.
   b[=a]lkr partition, bj[=a]lki beam, OS. balko, G. balken; cf.
   Gael. balc ridge of earth between two furrows. Cf. Balcony,
   Balk, v. t., 3d Bulk.]
   1. A ridge of land left unplowed between furrows, or at the
      end of a field; a piece missed by the plow slipping aside.
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            Bad plowmen made balks of such ground. --Fuller.
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   2. A great beam, rafter, or timber; esp., the tie-beam of a
      house. The loft above was called "the balks."
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            Tubs hanging in the balks.            --Chaucer.
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   3. (Mil.) One of the beams connecting the successive supports
      of a trestle bridge or bateau bridge.
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   4. A hindrance or disappointment; a check.
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            A balk to the confidence of the bold undertaker.
                                                  --South.
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   5. A sudden and obstinate stop; a failure.
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   6. (Baseball) A deceptive gesture of the pitcher, as if to
      deliver the ball. It is illegal and is penalized by
      allowing the runners on base to advance one base.
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   Balk line (Billiards), a line across a billiard table near
      one end, marking a limit within which the cue balls are
      placed in beginning a game; also, a line around the table,
      parallel to the sides, used in playing a particular game,
      called the balk line game.
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