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Webster 1913 Edition

Noun.

[Cf. G.

schwall

a sea swell, from

schwellen

to swell, E.

swell

Water breaking in upon the miners at their work; – so called among tin miners.

[Prov. Eng.]

Noun.

[See Well.] Among the tin miners, water breaking in upon the miners at their work.

swallet ‎(plural swallets)

(Britain) A sinkhole; a shakehole.
(Britain, dialect, dated, mining, tin mining) Water breaking in upon the miners at their work.