The definition of a chainman is someone who works with a surveyor to measure distances.
An example of a chainman is the man in the orange vest who helps measure a distance using a chain or tape measure.
a surveyor's assistant who measures distances with a tape measure or surveyor's chain: chainmen work in pairs
Either of the two persons who hold a surveyor's measuring chain.
- (surveying) One who wields a chain or measuring tape.