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Webster 1913 Edition

Noun.

;

pl.

Landmen

A man who lives or serves on land; – opposed to

seaman

(Eng.)

An occupier of land.

Cowell.

Noun.

A man who serves on land; opposed to seaman.

landman ‎(plural landmen)

Someone who lives or works on land, as opposed to a seaman.
In the United States, a person involved in determining, transferring, or managing mineral rights, to include oil (petroleum) and natural gas exploration, development, and production.