In times past it was often thought that ascended masters achieved their high state only after leaving their human body, but we now find in our timeline that we can achieve this state and remain living on the earth to help with the ascension of mankind.
To me an ascended master is one who is able to experience God's Love, Peace, Joy, Bliss, Creativity in every moment, no matter what earthly circumstances prevail in a given moment, and also remain anchored in a higher dimension even while living on earth (5th dimension or higher)...and when one has achieved a sufficiently high light quotient, an ascended master can transform their carbon based body into a crystalline silicon based 5th dimension body of Light.
Infinite Blessings & Energies of God's Love, Light, & Abundance to All of You,
Well, it did had its logic to call the dead ascended, as it is in a way in the literal meaning of the world as it would ensure that heightened state was considered permanent. Today we might know a little better, but master is not only existing on "higher" dimension, but should be able to teach that to others.