timolol Syllabification: (tim·o·lol)Pronunciation: /ˈtīməˌlôl, -ˌläl/Definition of timolol noun Medicine a synthetic compound that acts as a beta blocker and is used to treat hypertension, migraines, and glaucoma. Chemical formula: C13H24N4O3S Origin: 1970s: from tim- (of unknown origin) + (propran)ololtimolol in other Oxford dictionaries Definition of timolol in the British & World English dictionary