chiefly /ˈtʃiːf.li/adverb 2adjective 1forms 5 adverb2 •Especially or primarily; above all.Their relationship is chiefly professional.This is a term chiefly used by online gamers. •Mainly or principally; almost entirely. adjective1 •Of or relating to a chief.The maintenance of a perpetual fire came to be associated with chiefly or royal dignity. — 1890 formschieflier · more chiefly · chiefliest · chiefliest · most chiefly