The term 'flat occupant' is a general term used to describe someone who lives in a flat or apartment. The two most common words used to describe this type of person are 'TENANT' and 'RENTER'. A TENANT is someone who has a lease agreement with the landlord, while a RENTER is someone who pays rent on a month-to-month basis. Both tenants and renters are responsible for paying rent and taking care of the property they are living in.