1st fret E string
2nd fret A string.
That's a Diminished 5th, or a Tritone, (Which is derived from the fact that it's the interval made 3 whole steps from the root. Diatonic to Lydian and Locrian modes, though in Lydian, it's more correctly named as an Augmented 4th, but they're enharmonic.)
No question about it. Dissonant.
And, considering you have a high standard for music terms... There's no such thing as a minor b5. Or a Minor 5th for that matter. Perfect, Augmented, or Diminished (Tritone).
