MASTITIS Meaning of MASTITIS in English mas ‧ ti ‧ tis /mæˈstaɪtəs, mæˈstaɪtɪs/ BrE AmE noun [uncountable] a painful swelling of the breast or ↑ udder (=the part of some animals that gives milk) Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012