piano chord
E♭dim
E♭1G♭♭3B♭♭♭5
Two minor thirds stacked. The fifth is diminished, so it cannot be dropped without losing the chord.
Written the other way round it is D♯dim — the same twelve keys on a piano, a different piece of notation.
What is true of it
E♭dim is E♭, G♭ and B♭♭ — 1, b3 and b5 counted from E♭.
B♭♭ is a double flat, and it has to be: every letter from E♭ upwards is used once, so the b5 cannot be written any other way.