sink or swim
To succeed or fail by your own efforts, without help or interference from anyone else; fail if you don't work hard to succeed.
When Joe was fourteen, his parents died, and he was left by himself to sink or swim.
Tom's new job was confusing and no one had time to help him learn, so he had to sink or swim.
sit in
sit in on
To be a member; participate. To be a member of; participate in.
We're having a conference and we'd like you to sit in.
We want you to sit in on the meeting.
To attend but not participate. Often used with on.
Our teacher was invited to sit in on the conference.
sit on a volcano
sitting on a powder keg
To be in a place where trouble may start or danger may come suddenly.
Bob was in that part of South America before the revolution began. He knew he was sitting on a volcano.
The policemen who patrolled the big city slum area that summer were sitting on a volcano.
sitting on high cotton
Feeling pleased and happy; feeling successful.
The girls were sitting on high cotton because their basketball team had won the trophy.
sitting pretty
To be in a lucky position.
The new library is sitting pretty because a wealthy woman gave it $10,000 worth of reference books.
Mr. Jones was sitting pretty until his $25,000-a-year job was dropped by the company.
skate on thin ice
To take a chance; risk danger, disapproval or anger.
You'll be skating on thin ice if you ask Dad to increase your allowance again.
John knew he was skating on thin ice, but he could not resist teasing his sister about her boyfriend.
skating rink
Slippery road.
Attention all units - there's a skating rink ahead!
skeleton in the closet
A shameful secret; someone or something kept hidden, especially by a family.
The skeleton in our family closet was Uncle Willie. No one mentioned him because he drank too much.