In the UK all people who do these kinds of jobs(builder, plumbers, electricians etc) are called traders, I've never heard anyone use the word "tradesman".
Yes, but as I understand it, being a "sole trader" is different from being a "tradesperson". If you're an employed plumber, or you're a plumber with your own limited company, then you're a tradesperson but not a sole trader. If you do web sites or IT support on your own and without having set up a limited company then you're a sole trader but not a tradesperson.
The trouble with "trader" is that it usually means something else, namely someone who trades. A tradesperson doesn't trade; they practise a trade (= craft/profession).
Visit a UK builders' merchant or DIY store and they'll offer a 'trade account' with a 'trade discount' and 'trade deals' - they'll even sell you 'trade paint'
Ambiguous on a global scale? Maybe. Ambiguous when you're standing in a builders' merchant? Absolutely not.
....What definition? As a Brit, I'm telling you that's what we call people in these professions, anyone who comes to work on your house is a "trader" - you can choose to believe me or not lol.
Edit: and as another commenter pointed out, it's literally the government definition of someone running their own business - "sole trader".
Perhaps it is (or at least was) to some extent regional. Oxford English Dictionary does not have the sense of "trader" that's being discussed here. It does however have "tradesman = A man engaged in a trade or a skilled manual occupation". It also has a second sense for that word: "tradesman = A man engaged in trade or the sale of goods and commodities" and one of the examples for that sense, from 1906, is this sentence:
> ‘Tradesman’, which in the north is used to denote a workman who has learned a trade, while in the south it is made to apply to a man who runs a business.
That was more than a hundred years ago and things may have moved on a bit since then, and in any case that sentence is quoted as an example rather than a claim by the editors of the dictionary, but perhaps despite my current place of residence I'm a northerner at heart?