in·stru·men·tal/ˏɪnstrə`mɛntḷ; ˌɪnstrˈmentl◄/ adj 1 be instrumental in (doing) sth to be the thing or person that makes something happen 对某事起作用: a clue that was instrumental in solving the mystery 帮助解开这一谜团的一条线索 2 instrumental music is for instruments, not voices 用乐器演奏的，器乐的