1) When a single institution becomes so powerful, that it has total control over a certain commodity, service or industry. This can't actually exist, because it can't ever be truly 100%. At least, not until we live in a futurisitic
dystopia where the government/corporations/intelligent computers/big-headed aliens use mind control, rayguns and/or the Matrix to enforce control.
An example of an "Almost-monopoly" is Microsoft, who many people say have a monopoly of the Desktop PC Operating System market. This isn't true, as a small percentage of people use Macs or Linux
PC's. Hell, you can even use
FreeBSD as a desktop system.
2) A family game where people play shoes,
irons and cowboy hats masquerading as
CEO's vying for economic world domination. Based largely on luck, but skill/
know-how can also be used, as is proved by a sad person I know who spent his
young life getting good at the game so that, for once, he would be better than others at something. Usually, however, the game degenerates into petty fights and shouting matches.