An assessor is a person who is employed to calculate the value of something, or the amount of money that should be paid, for example in tax. [business]
2. countable noun
An assessor is a person who is an expert in a subject, especially someone asked to advise a court of law on that subject.
Two judges and six lay assessors sentenced White to life in prison.
3. countable noun
An assessor is a person who judges the performance of someone else, for example in an exam, at an interview or at a sporting event.