clack-boxn.(a) the box or chamber which contains the clack-valve of a pump;(b) in locomotive engines the box or cage enclosing the clack (see 5b);(c) dialect ‘the mouth which contains a nimble tongue’ (Forby).
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1849 J. WealeRudim. Dict. Terms Archit.i. 103/1Clack-box, in locomotive engines, the box fitted on to the boiler where a ball-clack is placed.