vitamin K1 n 1: a form of vitamin K [syn: {vitamin K1}, {phylloquinone}, {phytonadione}]
vitamin K1 \vitamin K1\ n. one of the two K vitamins, ({C31H46O2}). It is fat-soluble and occurs naturally as the trans isomer. Chemically it is 2-methyl-3-phytyl-1,4,-naphthoquinone. Syn: phylloquinone, phytonadione, antihemorrhagic vitamin.. [WordNet 1.5 +PJC] vitamin K2