hexadecimal Syllabification: (hex·a·dec·i·mal)Pronunciation: /ˌheksəˈdes(ə)məl/Definition of hexadecimal adjective Computing relating to or using a system of numerical notation that has 16 rather than 10 as its base. Derivatives hexadecimally adverb hexadecimal in other Oxford dictionaries Definition of hexadecimal in the British & World English dictionary