Petra \p(e)-tra, pet-ra\ as a girl's name is pronounced PEH-trah. It is of Greek origin, and the meaning of Petra is "rock". Feminine variant of Peter. Pier is used as a girl's name due to the 1950s actress Pier Angeli. Peta is a Dutch form.
Petra has 25 variant forms: Pella, Pernilla, Pernille, Perrine, Pet, Peta, Peterina, Peternella, Petria, Petrina, Petrine, Petronela, Petronella, Petronelle, Petronia, Petronija, Petronilla, Petronille, Petrova, Petrovna, Pier, Piera, Pierette, Pierrette and Pietra.
For more information, see also the related name Perri.