Surrender was the act of submitting to another power, typically on compulsion or demand.
In 2007, Cyber-Leader One, after arriving in the Earth of N-Space with an army of five million Cybermen from Pete's World, made a global broadcast from Torchwood Tower ordering the surrender of humanity. Nevertheless, the Cybermen were met with armed resistance, much to the Cyber-Leader's confusion. The Tenth Doctor explained:
They're not taking instructions. Don't you understand? You're on every street, you're in their homes, you've got their children! Of course they're going to fight.
Plain white flags were typically used in the event of a surrender. The Doctor, holding a sheet of A4 paper on a stick, met a group of Cybermen, jokingly apologising for not having an actual white flag. (TV: Doomsday)
In 2009, following a Dalek invasion of Earth which saw UNIT massacred, the Commander General of the United Nations broadcast a message announcing Earth's surrender to the New Dalek Empire. (TV: The Stolen Earth)