Of similar nature. Used to describe the heretical view that the Father, Son and Spirit are not each of the same divine nature

This term means similar (homoi) nature (ousious), in contrast to same (homoousios) or different (heteroousios) nature.  At the Council of Nicea, moderates suggested the term as a compromise between the homoousios of Athanasius and heteroousios) of Arius. Homoousios was chosen because it correctly defends that the Father and Son both share the same divine nature (John 1:1).