Entry 1 sense Webster, 1913 Frigidarium · Frig·i·da·ri·um · IPA /ˌfɹɪd͡ʒəˈdɛɹi.əm/ 01 n. The cooling room of the Roman thermæ, furnished with a cold bath. pl. Frigidaria ((#)) 1. The cooling room of the Roman thermæ, furnished with a cold bath.