1. It is a Greek word to inappropriately call someone a retard.
Its orientation comes from a building material (plaster) that is used to cover holes and make the walls smooth.
2. Also can be used to describe an ugly girl that has put a lot of plaster (makeup) on her face to cover up the ugliness. The next morning effect who the f_ck did i sleep with.
1. Ma ti stokos eisai!
You are a thick plank!
2. Kita poso stoko exei sto prosopo tis.
Look how much plaster she has on her face.