fundusPronunciation: /ˈfʌndəs/Definition of fundus noun (plural fundi /-dʌɪ/) Anatomy the part of a hollow organ (such as the uterus or the gall bladder) that is furthest from the opening. the upper part of the stomach, which forms a bulge above the level of the opening of the oesophagus (furthest from the pylorus). the part of the eyeball opposite the pupil. Origin: mid 18th century: from Latin, literally 'bottom'fundus in other Oxford dictionaries Definition of fundus in the US English dictionary