What is Assessor?

Legal Definition
Civil law. So called from the word adsidere, which Signifies to be seated with the judge. They were lawyers who were appointed to assist, by their advice, the Roman magistrates, who were generally ignorant of law. being mere military men. Dig. lib. 1, t. 22; Code, lib. 1, t. 51.

2. In our law an assessor is one who has been legally appointed to value and appraise property, generally. with a view of laying a tax on it.
-- Bouviers Law Dictionary
Legal Definition
An officer chosen or appointed to appraise, value or assess property. In civil and Scotch law. Persons skilled in law, selected to advise the judges of the inferior courts. Bell ; Dig. 1, 22; Cod. 1, 51 A person learned in some particular science or industry, who sits with the judge on the trial of a cause requiring such speclal knowledge and gives his advice. In England it is the practice in admiralty business to call in assessors, in cases involving questions of navigation or seamanship. They are called "nautical assessors," and are always Brethren of the Trinity House.
-- Black's Law Dictionary
Legal Definition
One whose function is to make an assessment.
-- Ballentine's Law Dictionary