term:

Counsel

counsel n

pl: counsel
[Old French conseil advice, from Latin consilium discussion, advice, council, from consulere to consult]
: lawyer : as
a : a lawyer participating in the management or trial of a case in court […to have the assistance of for his defense “U.S. Constitution amend. VI”] [a right to ]
b : a lawyer appointed or engaged to advise or represent a client in legal matters (as negotiations or the drafting of documents) compare attorney NOTE: A judge who has acted as counsel in a matter (as by advising an investigator) is disqualified from hearing the case.

of counsel
1 : assisting another lawyer in a case [was attorney of counsel]
2 : employed on a part-time basis [a tax attorney will move also and become of counsel “National Law Journal“]

vt -seled or: -selled
-sel·ing or: -sel·ling
: advise