Definition
To do something impalpably means to do it in a way that is difficult or impossible to perceive or grasp. It's something that's so subtle that you can't quite put your finger on it. Think of a very faint scent; you might detect it, but you can't easily describe it. It lacks clear definition, almost like a ghost. An impalpable change is nearly undetectable, while a palpable one is obvious and noticeable. Essentially, it describes an action that's elusive to the senses.