FILIOQUE
Etymology
Noun
filioque (uncountable)
(theology) The use of the Latin word filioque in the Western form of the Nicene Creed, to indicate that the Holy Spirit proceeds from both the Father and the Son (as opposed to the Eastern churches which believe the Spirit proceeds from the Father alone).
Source: Wiktionary
Fil`i*o"que, n. (Eccl. Hist.)
Definition: The Latin for, "and from the Son," equivalent to et filio,
inserted by the third council of Toledo (a. d. 589) in the clause qui
ex Patre procedit (who proceedeth from the Father) of the Niceno-
Constantinopolitan Creed (a. d. 381), which makes a creed state that
the Holy Ghost proceeds from the Son as well as from the Father.
Hence, the doctrine itself (not admitted by the Eastern Church).
Source: Webster’s Unabridged Dictionary 1913 Edition