a feeling or display of agreement and unity among a group of individuals who have common objectives or interests, a show of mutual support that produces or is based on a sense of community;
e.g. The students marched in solidarity with the protesters.
(noun)
a political phenomenon in Poland in the 1980s, involving a movement of trade unions that developed into a wider campaign in eastern Europe for political change and against communist regimes (used as "Solidarity");
e.g. He is best known as one of the prominent leaders of the Solidarity movement.