Definition from Wiktionary, the free dictionary
layman (plural laymen)
- layperson, someone who is not an ordained cleric or member of the clergy
- by analogy, someone who is not a professional in a given field
- Carmen is not a professional anthropologist, but strictly a layman.
- Let me explain it to you in layman's terms.
- a common person
- a person who is untrained or lacks knowledge of a subject
- a generally ignorant person
- lay-sister or lay-brother, person received into a convent of monks, following the vows, but not being member of the order
Derived terms 
Related terms 
someone who is not an ordained cleric
someone who is not a professional in a given field