Peasant oringally refered to the lowest class of society often small farmers, tenants, laborers who had to do hard manual labour to earn a small wage. They lived in poverty.
It is now used as an insult as well. The suggestion being the person or thing being insulted is simple minded, rustic, crude or of a low status then person who is using the insult.
It is mainly used in Australia.
'Dude, have you seen that person/object/place it is so peasant!'
'Peasants lived mainly on a diet of soup and bread with little meat.'