Question: To what does the term "epiclesis" refer?
Answer: The part of the Eucharistic Prayer that is the calling down of the Holy Spirit upon the offerings of bread and wine.
read more:
http://clarionherald.info/clarion/index.php/special-sections/year-of-renewal-the-mass/1060-the-epiclesis-the-calling-down-of-the-holy-spirit