I think that what IO540 is getting at is the literal translation of
an aircraft can stall in any attitude, any airspeed and any configuration
Let's take a sample aircraft, say a PA28 ('cause there's lots of them), trim it slightly nose down, final approach to a runway, nice shallow descent, say - 95 knots, clean or dirty (it matters not).
Now WITHOUT CHANGING THE ATTITUDE, SPEED OR CONFIGURATION - make that aircraft stall. How would you do that?