What does "filioque" mean?

Filioque: 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).