I. adverb Date: 14th century most importantly ; principally, especially , for the most part ; mostly , mainly , II. adjective Date: 1870 of or relating to a chief
CHIEFLY
Meaning of CHIEFLY in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012