sit in (on (something))

to go to a group event without being officially involved.

Do you mind if I sit in on your class?

• at no time
• at odds
• at odds with
• at odds with someone
• at odds with something
• at once
• at one fell swoop
• at one sitting
• at one time
• at one time or another
• a tongue-lashing
• a toss-up
• a tough act to follow
• a tough cookie
• a tough nut
• a tough nut to crack
• a tough row to hoe
• a tour de force
• a tower of strength
• at own game
• a toy boy
• at pains to
• at pains to do something
• at peace with
• at peace with something