Other forms: brows
Your brow is your forehead. It is also the top edge of a hill, where the ground stops rising.
The facial sense is slightly literary and appears in fixed phrases, since you mop your brow, knit your brow in worry and something makes you raise an eyebrow. The plural often means the eyebrows themselves. The landscape sense is very common in walking and driving, and coming over the brow of a hill is a standard phrase and a real hazard. Highbrow and lowbrow describe taste, from an old and discredited theory about skull shape.
Proto-Indo-European
*h₃bʰrúHs — brow
Proto-Germanic
*brūwō
Proto-West Germanic
*brāwu
Old English
brū
Middle English
browe
English, today
brow
From Middle English browe, from Old English brū, from Proto-West Germanic brāwu, from Proto-Germanic brūwō, from Proto-Indo-European h₃bʰrúHs (“brow”). Cognate with Scots broo (“brow”), Dutch brauw (“brow”), German Braue (“eyebrow”), Danish -, Norwegian Nynorsk - and Swedish bryn (“brow”), Faroese -, Icelandic brún (“brow”). See also mga brúad, txb pärwāne (“eyebrows”), Lithuanian bruvìs, Serbo-Croatian obrva (“eyebrow”), Russian бровь (“brow”), Ancient Greek ὀφρύς (“eyebrow”), Sanskrit भ्रू (“eyebrow”)), Persian ابرو (“eyebrow”), khw بروُ (“eyebrow”).
Etymology from Wiktionary, CC BY-SA