PER DIEM Meaning of PER DIEM in English [ pə:'di:ɛm , 'dʌɪɛm ]■ adverb & adjective for each day. ■ noun an allowance or payment made for each day.OriginC16: L. Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004