SLUCZK, a large and populous town in Russian Poland, in Lithuania, and formerly capital of a duchy of the same name; famous for three battles gained here by Constantine duke of Ostrog over the Tartars, in the reign of Sigismund I. It is seated on the river Sluczk, 72 miles south-east of Minski, and 70 south of Novogrodock. E. Long. 27. 44. N. Lat. 53. 2.