On thin ice
/ɒn θɪn aɪs/informal, neutralUK · US · AU · IE · CA
What does “On thin ice” mean?
On thin ice means in a risky situation where making one more mistake will cause serious trouble.
This idiom compares a dangerous situation to walking on frozen water that might break. If you take one wrong step, you can fall into deep trouble, just like falling into freezing water.
People usually say this as a stern warning. It shows that someone in authority, like a boss, teacher, or parent, is losing their patience with you.
When do people say it?
People use this phrase to warn someone that they are very close to getting into trouble.
“You are on thin ice, so do not be late for work again.”
Is it formal or informal?
Register: informal, neutral. It is most at home in both everyday conversation and professional writing. Most common in UK and US and AU and IE and CA.
Where does it come from?
The phrase comes from the real danger of falling through weak ice on a frozen lake. English writers have used this comparison since at least the sixteenth century.
Origin confidence: Well documented
How do you say “On thin ice” in other languages?
Last reviewed 2026-09-11