When you flash your high-beams at a passing car in order to warn them of (usually hidden) police presence nearby.
Jackie: Why'd that guy flash his high-beams at you?
Zach: He's giving me the high-beam heads-up. The 5-0 must be checking speeds up the street.
Zach: He's giving me the high-beam heads-up. The 5-0 must be checking speeds up the street.
by Andy Takai January 9, 2009