One engaged in the PRACTICE OF LAW; lawyer; advocate.
The term counsellor is commonly used interchangeably with attorney, except in a few states where the terms refer to lawyers of different ranks. In such states, an attorney may become a counsellor only after practicing law for a certain designated period of time and passing an additional examination.
Formerly, the Supreme Court of the United States made a distinction between a counsellor and an attorney. A counsellor was a lawyer who litigated on a party's behalf whereas an attorney at law did not do any trial work. This distinction is no longer made by the Court.