The Collaborative International Dictionary
Thick and threefold
Thick \Thick\ (th[i^]k), adv. [AS. [thorn]icce.]
Frequently; fast; quick.
Closely; as, a plat of ground thick sown.
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To a great depth, or to a greater depth than usual; as, land covered thick with manure.
Thick and threefold, in quick succession, or in great numbers. [Obs.]
--L'Estrange.
Wiktionary
thick and threefold
adv. (context dated English) In quick succession, or in great numbers.