Webster defines this type of knowledge as "a religious truth that is incomprehensible to reason and knowable only through divine revelation."

1.  Jesus Himself says "Unto you it is given to know the mystery of the kingdom of God:"  (Mark 4:11)

2.  The Apostle Peter says " Knowing this first, that no prophecy of the scripture is of any private interpretation.  For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost."  (2 Peter 1:20-21)

3.  The Apostle Paul says , " That the God of our Lord Jesus Christ, the Father of glory, may give unto you the spirit of wisdom and revelation in the knowledge of him:" (Ephesians 1:17)

Therefore, "revelation knowledge" is insight, understanding or explanation which is given to a individual by the Holy Spirit Himself concerning the Bible. It's sole propose is "to illume a man's soul, so he will not stumble."   If,  in fact , the Holy Spirit " so moved  on men to write the Bible, then only the Holy Spirit can interpret the Bible to an individual.  This is what is meant when one hers the phrase "revelation knowledge."  One can be relatively certain it wasn't gleaned from any seminary, denomination or theological dogma.  But,  rather, it was obtained by hours of Bible reading and study accompanied with hours of "praying in tongues," (communing with the Holy Spirit) .