splenomegalyPronunciation: /ˌspliːnə(ʊ)ˈmɛg(ə)li/Definition of splenomegaly noun [mass noun] abnormal enlargement of the spleen. Origin: early 20th century: from splen- 'spleen' + Greek megas, megal- 'great'splenomegaly in other Oxford dictionaries Definition of splenomegaly in the US English dictionary