The 27-year-old joins from Debreceni VSC, and spent last season on loan at Home Park.
Manager Ian Holloway said: "I am delighted that Peter has enjoyed it here and wanted to re-sign.
"He is outstanding, a magnificent professional. He is spot on with the way he lives, what he does and how he does it."
Argyle have also signed fellow Hungarian Krisztian Timar.
The centre-back, who also spent part of last season on loan at the club, joins from Ferencvaros in a £75,00 deal.
"He is a monster of a fella, and he more than played his part in last season," added Holloway.