The change follows industry pleas for greater clarity, after the nature and wording of the decision shocked and frustrated the cruise sector last week.
The new definition clears the way for Brits to take river cruises and appears to also allow sailings around the UK.
The FCO said: “Cruise ship travel means staying overnight for at least one night on a sea-going cruise ship with people from multiple households.
“Our advice against cruises applies to international travel on a ship that is exclusively for pleasure or recreation, providing overnight accommodation and other leisure facilities such as entertainment venues or swimming pools.
“Our advice does not include ferries or privately rented boats.
“The government will continue to review its cruise ship travel advice based on the latest medical advice.”
It advised those looking for more information on cruises in UK waters to contact the Department for Transport at maritimeengagement@dft.gov.uk
