There is no definition of the word "God" which Trinitarians can supply which is going to make any sense at John 17:3 or which will not contradict their own doctrine.

Jesus explains eternal life is to know "the only true God," that is, having a personal relationship with "the only true God. So WHO is that "only true God" in this verse? And once you have identified who that only true God is in this verse, can you claim that anyone else is that only true God whom you have identified? No, it cannot be done.

http://www.angelfire.com/space/thegospeltruth/trinity/verses/Jn17_3.html