I can’t find any dictionary entries for ‘pervisible’, although there are a number of uses of this word on the internet (some of them typographical anomalies; many of them in Spanish). ‘Per’ as a prefix indicates ‘very’ or ‘utterly’, as in ‘perfervid‘, so, logically, ‘pervisible’ would mean ‘highly visible’, ‘unmistakable’.

One of the uses of ‘pervisible’ I found was the text of the book in which I originally discovered it. So here is the word in context:

Vanye looked up, the sword clenched in his fist; and Roh’s shape drifted amid the light and the sound, pervisible, larger than life.

Source: The Chronicles of Morgaine, C J Cherryh.