1) The identifying code letters or numbers of a radio or television transmitting station, assigned by a regulatory body. Also called call sign or call letters.

2) (military) code word for aircraft, ship, etc, used in radio communications.
Dark 87 this is Havoc 12, switch to 11175 and vector out to DZ.
by IRISHREPUBLICANARMY December 26, 2003
Get the callsign mug.
call sign
noun: callsign
a message, code, or tune that is broadcast by radio to identify the broadcaster or transmitter.
NOT how you refer to someone.
"hey, callsign four_leaf, that's a pretty cool username"
"thanks, but you can call me "four leaf" or "Daniel"

"can't i just call you "callsign"?"
"fucking no, you cannot"
by Callsign Four_Leaf May 9, 2020
Get the Callsign mug.
A nickname earned by a Carleton Engineer that is inscribed on their flightsuit and/or F.I.T shirt. Callsigns are usually given to commemorate outrageous acts during frosh week, but can also be based off a recurring personality trait, or something completely irrelevant. Callsigns are traditionally regulated by the flightsuits, the self described militant wing of the Engineers at Carleton. Callsigns is also a drinking game where the participants must remember the action and callsign of the person before and after them in sequence, with varying difficulties as the "level" of the game increases.
Sebastian: "Why does Chris have the callsign "Sexbot"?"
Luke: "Well, he created a robot costume out of pizza boxes, made a giant pink cardboard penis for his costume, and walked around the market like that for the night."
by Null_01 April 7, 2010
Get the Callsign mug.
KC2THU - Assigned to Cthulhu when he passed his ham license test.
I worked Cthulhu on 20 meters last night. He used his new callsign of Cthulhu.
by K2ORS SK February 2, 2008
Get the callsign of cthulhu mug.