Computer system: A somewhat more technical term for describing a rig, usually including a processor, hard disk, monitor, RAM, cards, etc.
A weather system: An area that has an airmass of notably high or low air pressure; can be affected by thermodynamic interactions with the atmosphere, bodies of water, etc.
System: In general, anything that unifies more than one thing or organizes them. Eg: healthcare system, etc.
System (of a Down): System is often used as an abbreviation for the name of this kick-ass band because you want to save time for discussing how awesome they are.
Hey Jim, I just made a new system for getting my homework done so I can check all the high-pressure systems on my expensive new system, while listening to System!