phytohaemagglutininPronunciation: /ˌfʌɪtə(ʊ)hiːməˈgluːtɪnɪn/ (US phytohemagglutinin)Definition of phytohaemagglutinin noun [mass noun] Biochemistry a plant protein, especially that extracted from the French bean, that causes red blood cells to clump together. phytohaemagglutinin in other Oxford dictionaries Definition of phytohaemagglutinin in the US English dictionary