timololPronunciation: /ˈtɪməlɒl/Definition of timolol noun [mass noun] Medicine a synthetic compound which acts as a beta blocker and is used to treat hypertension, migraine, and glaucoma. Chemical formula: C13H24N4O3 Origin: 1970s: from tim- (of unknown origin) + (propran)ololtimolol in other Oxford dictionaries Definition of timolol in the US English dictionary