Tabula rasa comes from Latin where it meant blank slate. This is how it is used today as well, though there are nuanced differences in the actual English definition. It can refer to something in an unaltered state, or the mind of a person before it is influence by others.
Rasa can be pronounced with an ess sound or a zee sound.
The plural of tabula rasa is tabulae rasae which is spelled differently but keeps the Latin -i pronunciation \-ˌlī-ˈrä-ˌzī, -ˌsī\ (tab u lye raz i).
A fresh start is within reach, but as Sarah undergoes the final treatment to render her a tabula rasa — a blank slate — the hospital is invaded by special-ops forces, and Sarah must fight to stay alive without even knowing exactly who she is. [Richmond Times-Dispatch]
Still, the dream of tabula rasa in the heavens is hard to dislodge from human yearning. However, as Jai Galliot reminds us, dreams of solitude might dissolve as soon as we bump into our first galactic neighbour. [ABC Online]
James, the protagonist, is a generic teenage boy whose only distinction lies in his having been raised in a better Goodhouse; the system has tried to make him tabula rasa and for the most part succeeded. [The New York Times]
According to followers of Locke, who considered human beings as being tabulae rasae at birth on which knowledge gained through the senses would be inscribed, people who were deaf were capable of as much education as their senses would allow. [Branson]