Of course one can't talk of monobrows (or unibrows, as they are sometimes known) without mentioning Frida Kahlo, so here she is:
Having said all that, while half the world is blackening its brows to make them more obvious, the rest of us are plucking them for fear of attracting the attention of birds searching for nesting material. Still, even if you live in a society where eyebrows are completely plucked, or perhaps where faces are veiled and mirrors illegal, then unless you live in an endless plain then you're all right because of course hills have brows, too, and so do the tops of mine shafts and pitheads; and someone who's browbeaten, that is frightened by threats or daunted by unkindness, will probably have a troubled brow, which extends meaning of brow to the whole forehead.
The nice thing is that the brow-of-a-hill word is the same word as the eyebrow sort of a brow.
It makes me regard the trees that fringe my hilly horizon in an entirely new light.
Spot the Frippet: brow. This word comes from the Old English brū, is related to Old Norse and Lithuanian words, and goes right back to the Sanskrit bhrūs.