The Collaborative International Dictionary of English v.0.48:

Boast \Boast\, v. i. [imp. & p. p. Boasted; p. pr. & vb. n.
   Boasting.] [OE. bosten, boosten, v., bost, boost, n.,
   noise, boasting; cf. G. bausen, bauschen, to swell, pusten,
   Dan. puste, Sw. pusta, to blow, Sw. p["o]sa to swell; or W.
   bostio to boast, bost boast, Gael. bosd. But these last may
   be from English.]
   1. To vaunt one's self; to brag; to say or tell things which
      are intended to give others a high opinion of one's self
      or of things belonging to one's self; as, to boast of
      one's exploits courage, descent, wealth.
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            By grace are ye saved through faith; and that not of
            yourselves: . . not of works, lest any man should
            boast.                                --Eph. ii. 8,
                                                  9.
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   2. To speak in exulting language of another; to glory; to
      exult.
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            In God we boast all the day long.     --Ps. xliv. 8
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   Syn: To brag; bluster; vapor; crow; talk big.
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