sit in for (one)
1. verb To participate in a non-violent protest in which participants occupy a particular space and refuse to move. Students have been sitting in since Monday to protest discriminatory enrollment practices.
2. verb To attend something as a spectator or visitor, rather than a regular or full participant. Typically followed by "on (something)." They invited me to sit in on one of their meetings to see how things normally progress. I didn't earn any credit for it, but sitting in on the class gave me a lot of useful information that I could apply to my business.
3. verb To temporarily act as a substitute for someone else, especially in a meeting or discussion-based activity. Typically followed by "for (someone)." Hi, everyone, I'll be sitting in for Mike in today's meeting. He had to fly back to Memphis last night for a family emergency. Our manager is out of the office today, so Mary will be sitting in instead.
4. noun A non-violent protest in which participants occupy a particular space and refuse to move. As a noun, the phrase is hyphenated. Students have organized a sit-in to protest discriminatory enrollment practices.
sit in for (one)
To act as a temporary substitute for one, especially in a meeting or discussion-based activity. It was decided that I would sit in for the boss at the board meeting. I can't believe they sent an intern to sit in for the mayor on the climate committee.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
sit in (on something)
to attend something as a visitor; to act as a temporary participant in something. Do you mind if I sit in on your discussion? Please do sit in.
(for someone) to act as a substitute for someone. (Usually involves actual sitting, such as at a meeting.) I am not a regular member of this committee. I am sitting in for Larry Smith. Do you mind if I sit in? My representative can't be here.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
1. Attend or take part as a visitor, as in My son's jazz group asked me to sit in tonight. It is often put as sit in on, as in They asked me to sit in on their poker game. [Mid-1800s]
2. Take part in a sit-in, that is, an organized protest in which seated participants refuse to move. For example, The students threatened to sit in unless the dean was reinstated. [c. 1940]
3. sit in on. Visit or observe, as in I'm sitting in on his class, but not for credit. [Early 1900s]
4. sit in for. Substitute for a regular member of a group, as in I'm just sitting in for Harold, who couldn't make it.
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
1. To be present or participate as a visitor at a discussion or music session: The professor allowed me to sit in on one of her lectures. A guitarist will be sitting in with the band today.
2. To take part in a sit-in or similar organized protest: The protesters sat in at the construction site.
3. sit in for To act as a substitute: She will be sitting in for the usual news anchor, who is away on vacation.
The American Heritage® Dictionary of Phrasal Verbs. Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.