Learner's definition of LAYMAN
1 : a person who is not a member of a particular profession
For a layman, he knows a lot about the law.
a medical journal written in language that is clear to the layman [=clear to someone who is not a medical professional]
The process was explained to us in layman's terms. [=in simple language that anyone can understand]
2 : a person who belongs to a religion but is not a priest, minister, etc.