GNU Collaborative International Dictionary of English

Found one definition

1.       
   Clack (?), v. i. [imp. & p. p. Clacked (?); p. pr. & vb. n. Clacking.] [Prob. of imitative origin; cf. F.claquer to clap, crack, D. klakken, MHG. klac crack, Ir. clagaim I make a noise, ring. Cf. Clack, n., Clatter, Click.]
   1. To make a sudden, sharp noise, or a succession of such noises, as by striking an object, or by collision of parts; to rattle; to click.
   
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   We heard Mr.Hodson's whip clacking on the ahoulders of the poor little wretches. Thackeray.
   
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   2. To utter words rapidly and continually, or with abruptness; to let the tongue run.
   
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