429 ("Four-two-nine") — Gay. Spells G-A-Y on a phone. Used as a codeword by gay people. It's opposite, straight, is encrypted as "924" ("Nine-two-four").
"We've got a 429 at 10 o-clock!" , "Watch out, he is a 924!"
Originally derived from dialing “GAY” on a telephone, the word is now commonly used by railroaders when identifying homosexual train crews and foamers.
Conductor: You see that foamer standing at the end of the station platform over there?