There are a few synonyms for the word "Southdown". One such term is "Downland", which refers to the rolling hills or high plateau areas in southern England where the Southdown sheep breed originated. Another synonym is "Southdown breed", which is a specific type of domesticated sheep known for their wool and meat. Additionally, "South Downs" is another term used to describe the Southdown area of southern England that encompasses many of the rolling hills and valleys where the breed thrives. Other synonyms that could be used to describe Southdown might include "Yorkshire Down" or "Hampshire Down", which are similar breeds that also originated in the southern English region.