ˌfellow ˈtraveller British English,
fellow traveler American English noun [countable] someone who supports and agrees with the beliefs of an organization, such as the Communist Party, but does not belong to it – used to show disapproval
[TahlilGaran] Dictionary of Contemporary English ▲
fellow traveller n. A sympathizer with a political movement who does not officially belong to the political party in question.
Many Germans after World War II were innocently accused of being fellow travellers of Nazism. During the McCarthy era, many Americans were accused of being Communist fellow travellers. [TahlilGaran] English Idioms Dictionary ▲