What people mean by the formless svarūpa of the Mother,—they mean usually her universal aspect. It is when she is experienced as a universal Existence and Power spread through the universe in which and by which all live. When one feels that Presence one begins to feel a universal peace, light, power, bliss without limits—that is her svarūpa. One meets this more often by rising in consciousness above the head where one is liberated from this limited body consciousness and feels oneself also as something wide, calm, one self with all beings—free from passion and disturbance in an eternal peace. But it can be felt through the heart also—then the heart too feels itself wide as the world, pure and blissful, filled with the Mother’s presence.
There is also the Mother’s personal and individual presence in the heart which brings immediately love and bhakti and the sense of a close intimacy and personal oneness.
Ref: The Mother with Letters on The Mother