ISOSEISMAL Meaning of ISOSEISMAL in English [ ˌʌɪsə(ʊ)'sʌɪzm(ə)l ]■ adjective Geology denoting a line on a map connecting places where an earthquake was experienced with equal strength.Derivativesisoseismic adjective Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004