" sit-in "

[Noun]  | "sit-in" | \ ˈsit-ˌin \

1: sit-down

2: an act of occupying seats in a racially segregated establishment in organized protest against discrimination

3: an act of sitting in the seats or on the floor of an establishment as a means of organized protest

Origin: 1936 ;

[Verb]  | "sit in" 

1: to take part in or be present at a session of music or discussion as a visitor —often used with on

2: to participate in a sit-in

Origin: 1936 ;

[Idiom]  | "sit in judgment" 

1: to say whether or not someone or something is morally good, proper, etc.

[Phrasal verb]  | "sit in on" 

1: to attend (something, such as a class or meeting) without officially participating

[Verb]  | "sit in" 

[Noun]  | "sit-in"