An agent. In a suit the counsel or solicitor conducting it is called the party's procurator. Local attorneys in the Sheriff Courts are called Procurators of Court.

Definition source
Kinnear, J. B., Digest of House of Lords Cases Decided on Appeal from Scotland, 1709-1864 — Glossary of Scottish Law Terms (Edinburgh, 1865). Public domain.

Legal Subject: Procurator

Case Date Legal Subject Abstract
Knox v. Faculty of Procurators in Glasgow 1798 Procurator, Charter, Faculty, Penalty, Interlocutor, Contract Hugh Knox, Writer in Glasgow, petitioned the Court against the Faculty of Procurators in Glasgow, seeking to remit their regulation that imposed £30 of entry money upon him on the grounds that his apprenticeship had ended before the regulation was enacted and the charge was therefore retrospective and oppressive. The Faculty answered, defending the regulation against his claims.
Marshall v. Youngson 1798 Procurator, Court of Session, Agent, Interlocutor, Clerks of Session, Jurisdiction James Marshall, Writer to the Signet, petitioned the Court to alter a recent interlocutor respecting the offices held by Alexander Youngson. Youngson answered, defending his concurrent practice as procurator before the High Court of Admiralty and Writer to the Signet on the ground that the two roles were not incompatible. The dispute turned on whether the office of Writer to the Signet could be held consistently with acting as a procurator in the Admiralty Court.
Smyth v. Bushby 1794 Advocation, Process, Sist, Procurator, Adjudication, Court of Session In the bill of advocation between Smyth and Bushby, the sheriff-clerks of Scotland moved the Court to recall an order that had permitted transmission of inferior court processes to the bill-chamber without warrant or security. The Clerks to the Bills opposed this relief, contending that the practice of granting two successive orders for production of inferior court process in such bills had been uniform since 1765.