OMICRON Meaning of OMICRON in English [ ə(ʊ)'mʌɪkrɒn ]■ noun the fifteenth letter of the Greek alphabet ( Ο , ο ), transliterated as ‘o’.Originfrom Gk o mikron 'small o'. Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004