homoiousian
One of the Semi-Arians of the 4th century who held that the Son was of like, but not the same, essence or substance with the Father.
historical
The Greek word, which was chosen to express this mysterious resemblance, bears so close an affinity to the orthodox symbol, that the profane of every age have derided the furious contests which the difference of a single diphthong excited between the Homoousians and the Homoiousians.
Where it comes from
From Ancient Greek ὁμοιούσιος (homoioúsios), from ὅμοιος (hómoios, “like, similar”) + οὐσίᾱ (ousíā, “essence”).
Adapted from the Wiktionary entry homoiousian (CC BY-SA 4.0).