An instrument approach system used in aviation. Short for Localiser and can also be used for the LNAV. Some planes may have APP which is a combination of the LOC function and the G/S (Glide Slope). APP is short for Approach. The LOC or ILS arms the G/S to the runway. Each runway at an airport typically has different ILS numbers (Set in your NAV 1 or 2 radio frequency), but some major airports have it in both directions such as KLAX. For missed approaches, use your BC (Back Course).
You buy a new Ford Mustang. After you have sent a picture of it to your brother in law at his request, he texts to you, "looks like we're gonna have to change your nickname to mustang sally". You text back the acronym "LOC". After a moment you should end up with a question mark from him indicating that he doesn't understand. You now have the opportunity to elaborate, "laughing out of courtesy...because that's all anyone ever does at your stupid jokes."
If someone's sarcasm or snarkiness doesn't actually make you LOL...use LOC.
2) (n) Crazy one, from the Spanish "loco", often used for friends or locals in a positive way.
3) (n) Lock or locks, as in Jheri-curls, but always pronounced with the long o as in "go".
4) (v) To "go loc" means to get ready for a drive-by or to shoot someone. This means putting on dark glasses, skullies, caps and generally getting hard to identify.