Well to me anywhere you trade anything is an exchange. And if you want to get all technical about it then it is still an exchange because the broker is helping you buy an sell stocks in EXCHANGE for fees. When you look up the word exchange in the dictionary, it means to trade. Just because its not a global exchange doesn't mean it's not any kind of exchange.
Walmart can be considered an exchange, your exchanging money for products. A yard sale can be considered an exchange, just because there are no charts to look at when you buy something doesn't mean it isn't.
You guys really need to get off your high horses and start taking what I'm saying with more consideration.
Believe it or not, a lot of people here are taking what you are saying with more consideration, otherwise, they would have never bothered to respond in the first place.
An exchange is where the actual trade happens between 2 parties or their respective agents (In the case of securities exchanges, they are called brokers or agents or authorized participants or authorized person, all are principally meaning the same).
Trades do not actually get executed @RH, Robinhood as well as other brokers send orders on behalf of their customers to the relevant exchange to get them executed.
If Robinhood matches orders between buyers and sellers themselves, they would definitely be an exchange, but in reality, they don't, hence they are not considered an exchange.
Even your definition of Walmart by considering it as an exchange is not very accurate. Walmart, Amazon, etc...are more of marketplaces rather than exchanges. It's true that @Walmart or @Amazon, you do exchange money for products/services, so from this angle (and by the exact wording), they can be considered exchanges where there is one seller and multiple buyers. Amazon is probably more close to an exchange than Walmart since Amazon allows almost anyone to setup their shop and sell their products, though not accurate because Amazon themselves are a seller as well, which pretty much have a conflict of interest, but that's a different topic.
And who said that you can't have charts for Amazon products? If you check camelcamelcamel.com, you will find that they chart Amazon product prices for you.
I guess you are taking the discussion from a precise wording view, while most of the people here are taking it from the real world practical perspective, but I believe you are on the wrong side of the discussion as this is not really an English language forum, it's a traders forum.
Cheers