(Sanskrit) From nir (without) guna (quality).
"The impersonal aspect [of God] (Nirakara, Nirguna) is called Brahman, or ‘unknowable’ by Herbert Spencer, ‘will’ by Schopenhauer, Absolute Noumenon by some ‘substance’ by Spinoza. The personal aspect (Sakara) of that Being is termed ‘Ishvara’ or Allah, Hari, Jehova, Father in Heaven, Buddha, Siva, etc. Just as vapour or steam is formless, so also God is formless in His unmanifested or transcendental state." - Swami Sivananda