Definitions for peta-
Random House Webster's College Dictionary
a combining form used in the names of units of measure equal to one quadrillion (1015) of a given base unit.
Origin of peta-:
In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 10. Symbol: P
Origin: Based on penta- with the middle letter removed, but the previously coined prefix tera- came from Greek teratos, which means monster.