What is a waiver of arraignment?

Answer 1

An "arraignment" is a court appearance in which the defendant is formally charged with a crime and asked to respond by pleading guilty, not guilty or nolo contendere. Other matters often handled at the arraignment are arranging for the appointment of a lawyer to represent the defendant and the setting of bail.

It appears you've already obtained the services of an attorney who has "waived" or declined the arraignment hearing as he does not wish to congest the court schedule since he is already aware of the charges against you...therefore, he's waived arraignment.