expression, godan verb (-ru)
be on one's guard; keep one's wits about one; be wary
Idiomatic expression meaning to stay alert and not be deceived; literally 'to put saliva on one's eyebrows', from the folk belief that spitting on one's eyebrows wards off foxes and badgers that trick people.
See also: 眉に唾をつける
彼の話はうますぎるから、眉に唾を塗って聞いたほうがいい。
His story sounds too good to be true, so you'd better listen with a grain of salt.
ネットの情報には眉に唾を塗ってかかれ。
Take online information with a pinch of salt.