an organized passive protest, esp. against racial segregation, in which the demonstrators occupy seats prohibited to them, as in restaurants and other public places.

any organized protest in which a group of people peacefully occupy and refuse to leave a premises

Sixty students staged a sit-in outside the dean's office.

sit-down strike.

noun

complaint , demonstration , fast , grievance , love-in , march , passive resistance , peace march , peaceful protest , protest , rally , revolt , riot , sit-down , strike , walkout , display