You are correct -- a monopoly is when a single entity maintains total industry control. Of the companies you listed, none of them match this definition.
Google > There are are numerous search engines.
Here is a list of the top 10. Not a monopoly.
Microsoft > There are numerous operating systems. OS X, iOS, Ubuntu, Redhat, Debian, GNU, ArchLinux, Linux Mint, Puppy Linux, openSUSE, Fedora, Mageia, CentOS etc. Not a monopoly.
Facebook > There are numerous social media sites. MySpace, Twitter, Reddit, Tumblr, Flickr, Instagram, Google+, Pinterest, etc. Not a monopoly.
Monsanto > There are numerous genomics companies. Archer Daniels Midland Company, Dow Chemical Company, Evogene, are a few major ones. Not a monopoly.
YKK > This is a Japanese company and not an American one. Nonetheless it has competition in the form of Arconic, Rio Tinto Alcan, and Talon International. Not a monopoly.
AB InBev > This is a Belgium company. Nonetheless it has competition in the form of Carlsberg Breweries, Heineken, Sabmiller Limited, and many others. Not a monopoly.
Simmons > This is a UK law firm. They do not control the entire industry either, and have major competitors in the form of Clifford Chance LLP, Freshfields Bruckhause Deringer, and Norton Rose. Not a monopoly.
Additionally, controlling 55% of a market share does not indicate a monopoly when there are 5,903 competing firms in the financial industry. Just because not all financial institutions in the United States are not consumer-facing does not mean that they aren't competition.
There is no resource scarcity to prevent a consumer from switching to a bank with less market share if they choose to do so. This is not an oligopoly.