The famous line from the General Prologue and something to aspire to for the rest of us.
In terms of meaning 'veray' is from the French of which the modern version is 'vrai' - meaning 'true', 'parfit' you can understand from the modern French 'parfait' for 'perfect' and 'gentil' which would translate to a modern 'gentleman' or someone 'noble' in character.
So, 'He was a true perfect noble knight.'
With thanks to thnidu for some corrections to the above.