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1.
Another form of saying hi. One must raise both of their eyebrows when coming across someone on the opposite side of the direction you are heading towards.

It's usually used when one is too lazy or in a rush to wave or say hello.
Joe and Jim were quickly walking to class before the bell. They both maintained their pace to class by making eye contact with one another and made a hibrow.
by PikaJAR November 04, 2010