(1):

(n.) One of those (as in the 16th century) who denied the visibility of the church.

(2):

(a.) Incapable of being seen; not perceptible by vision; not visible.

(3):

(n.) An invisible person or thing; specifically, God, the Supreme Being.

(4):

(n.) A Rosicrucian; - so called because avoiding declaration of his craft.