simply its mean for most of us:

Open Source

may be the same characters have other meaning , but the most popular is open source.

And these is some other meaning for OS characters:
http://en.wikipedia.org/wiki/Os
by peter edin August 27, 2008
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Backwards for so so. Originally from The Simpsons.
Homer: So, how was it?
Bart: os os.
Homer: What?
Bart: That's backwards for so so.
by gak September 15, 2006
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Is attracted to kpop or hot korean men :).
oseli is obbsessed with so much kpop she dosent pay attention to people
by lovleyrose June 3, 2020
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Kid who swears and drinks a lot and is not liked by Hometown
That kid is such an OS
by TenIsGOAT August 16, 2019
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Operating system. Simply, a program that runs your computer. Examples of an operating system are CP/M, DOS, Windows, Mac OS, Linux, and Palm OS, though there are many more. One will oftentimes become overly attached to their OS, preaching it as though it were a religion and shunning all who use anything even slightly different.
Man: My OS of choice is Windows XP.
Woman: My OS of choice is Mac OS X.
Man & Woman: (killing eachother)
Supa-Nerd: My OS of choice is CP/M! 8086 FOREVAH!!!
by Chow October 28, 2004
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Abbreviation for Operating System

A good list of popular Operating Systems are listed here (taken from "www.bellevuelinux.org"):
AIX
Amiga
BeOS
Darwin
FreeBSD
FreeDOS
GNU/Hurd
HP-UX
IRIX
JavaOS
Linux
Mac OS X
Microsoft Windows
MINIX
MS-DOS
NetBSD
OpenBSD
Palm OS
QNX
SkyOS
Solaris
TRON
Tru64

An operating system is the main software that runs a computer, without an operating system a computer is almost useless.

There is no best operating system, they all have their advantages/disadvantages and were all developed with some kind of goal in mind.
1: All the company's servers used Unix (OS), but now they use Linux (OS).

2: George had a quadruple boot with multiple OSs running on his PC, it ran Microsoft Windows Vista Ultimate, Mac OS X Leopard, and two flavors of Linux.
by Klienmahn November 8, 2007
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