Willimantic (wĭləmăn`tĭk), former city in the town of Windham, Windham co., Conn., at confluence of Willimantic and Natchaug rivers, which there form the Shetucket River; inc. as a borough 1833, as a city 1893, uninc. 1983. Cotton spinning was established there in 1822, and Willimantic became known as the Thread City because of the location of the American Thread Co. factory there. The factory closed in 1985. Eastern Connecticut State Univ. and a textile and history museum are there.