Although I have no experience with any extensive program of meditation, it is clear to me that "vibrations" is a word given to a certain aspect of internal experience that is "subtle" in the sense that a person would probably not notice it without spending quite a few hours in mediation or at least in paying close attention internal experience.

ADDED. Because any two human minds have so much in common, it is possible to have a worthwhile discussion about various aspects of internal experience. Although it's a lot harder to catch someone in a lie about their internal experience than it is to catch them in a lie about external reality, that does not prevent worthwhile sharing of knowledge about internal experiences.

ADDED. Great writing, BTW, PyryP (author of grandparent).