to give someone 'the eyebrow' is to raise ones eyebrows at the recipient then flick their gaze back and forth from the recipient towards another person in a suggestive manner.
Looking at your friend then giving them the eyebrow to the guy/girl he/she fancies or is fancied by.
A suden, very short, painless, harmless spasm to the eyebrows. Unable to control but only lasts half a second-two seconds. Usually only occurs very occasionally
1: That was weird.
2: What? I didn't see anything.
1: I just had an eyebrow attack