No, that's not accurate. "Poaching" is a strategy used by employers in which specific companies are targeted from which to acquire employees. By your definition of "poaching", virtually all hiring of software engineers would be "poaching", because most software engineers are already employed.
Company X hiring an inbound lead that happens to be from company Y: not poaching.
Company X hiring a recruiter-based lead that happens to be from company Y: not poaching.
Company X instructing recruiters to draw up a list of employees of company Y and target them individually by persuading them to leave their jobs: poaching.
This is a good clarification. I should have been clearer. In partciular, I should have specified (in my articularion) anyone employed under contract (not at-will).+
The #3 case here is probably the best reference here for a definition of contemporary usage.
The frission around the ~negative connotation may be hard to understand without the context of entymology. Poaching indeed has a long history in the English language and its "literal" meaning involves the taking of "other's property" by way of hunting. The nexus of "others property" here is important. Originally this was birthrights to game and chattle rights to spouse and since this was before the industrial revolution, employment would be similarly duty bound.
So, to poach is to hunt, or to head-hunt, against other's formal (eg contractual) rights. It has been along time since then and the term is now idiomatic. So, if you want to understand the "subtlety" or the "frission", it probably helps to understand the entymology.
But, as noted above, this doesn't help you to understand contemporary usage as much as somthing more detailed on that subject. So, defer to the above comment.
This is a good example of HN comments getting all the points out on the table from different views.
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+ Years ago, when head-hunting was "executive recruiting", most of these folks would have been under contract, for example. Or be partners in a law firm or bank. Again, the world has moved on and recruiting now is not limited to high-level execs, or people in company careers that might otherwise be 30 years long or whatevs.
Company X hiring an inbound lead that happens to be from company Y: not poaching.
Company X hiring a recruiter-based lead that happens to be from company Y: not poaching.
Company X instructing recruiters to draw up a list of employees of company Y and target them individually by persuading them to leave their jobs: poaching.