Almost never used alone in modern Chinese — appears in two important set phrases:
好高骛远 hàogāo-wùyuǎn 'aim too high, chase the far' (over-ambitious / unrealistic), and
心无旁骛 xīnwúpángwù 'heart with no side-rushing' (single-minded focus). The radical
马 (horse) hints at the original 'galloping' image.