1. [n]  an illegal pitching motion while runners are on base
2. [n]  one of several parallel sloping beams that support a roof
3. [n]  something immaterial that interferes with or delays action or progress
4. [n]  the area on a billiard table behind the balkline; "a player with ball in hand must play from the balk"
5. [v]  refuse to comply

BALK is a 4 letter word that starts with B.

1. \Balk\, 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. i., 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.
            Bad plowmen made balks of such ground. --Fuller.
   2. A great beam, rafter, or timber; esp., the tie-beam of a
      house. The loft above was called ``the balks.''
            Tubs hanging in the balks.            --Chaucer.
   3. (Mil.) One of the beams connecting the successive supports
      of a trestle bridge or bateau bridge.
   4. A hindrance or disappointment; a check.
            A balk to the confidence of the bold undertaker.
                                                  --South.
   5. A sudden and obstinate stop; a failure.
   6. (Baseball) A deceptive gesture of the pitcher, as if to
      deliver the ball.
   {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.
   

2. \Balk\, v. t. [imp. & p. p. {Balked} (?); p. pr. & vb. n.
   {Balking}.] [From {Balk} a beam; orig. to put a balk or beam
   in one's way, in order to stop or hinder. Cf., for sense 2,
   AS. on balcan legan to lay in heaps.]
   1. To leave or make balks in. [Obs.] --Gower.
   2. To leave heaped up; to heap up in piles. [Obs.]
            Ten thousand bold Scots, two and twenty knights,
            Balk'd in their own blood did Sir Walter see.
                                                  --Shak.
   3. To omit, miss, or overlook by chance. [Obs.]
   4. To miss intentionally; to avoid; to shun; to refuse; to
      let go by; to shirk. [Obs. or Obsolescent]
            By reason of the contagion then in London, we balked
            the ?nns.                             --Evelyn.
            Sick he is, and keeps his bed, and balks his meat.
                                                  --Bp. Hall.
            Nor doth he any creature balk, But lays on all he
            meeteth.                              --Drayton.
   5. To disappoint; to frustrate; to foil; to baffle; to
      ?hwart; as, to balk expectation.
            They shall not balk my entrance.      --Byron.
   

3. \Balk\, v. i.
   1. To engage in contradiction; to be in opposition. [Obs.]
            In strifeful terms with him to balk.  --Spenser.
   2. To stop abruptly and stand still obstinately; to jib; to
      stop short; to swerve; as, the horse balks.
   Note: This has been regarded as an Americanism, but it occurs
         in Spenser's ``Fa["e]rie Queene,'' Book IV., 10, xxv.
               Ne ever ought but of their true loves talkt, Ne
               ever for rebuke or blame of any balkt.
   

4. \Balk\, v. i. [Prob. from D. balken to bray, bawl.]
   To indicate to fishermen, by shouts or signals from shore,
   the direction taken by the shoals of herring.