Here is a list of idiomatic expressions formed around words beginning with O.
Sow your wild oats
To sow your wild oats is to have too many casual sexual relationships when you were young.
Odds and ends
Various small items that are not part of a larger set
Off and on
Now and then
Be on the offensive
When someone is on the offensive, they are ready to act aggressively.
- The minister seemed to be on the offensive.
If something is on offer, it is available for purchase at a reduced price.
In the offing
If something is in the offing, it is likely to happen soon.
- A new education policy is in the offing.
Be one up on
When you are one up on somebody, you have an advantage over them.
One and all
- They have invited one and all.
One and only
If something is regarded as being one and only, it is unique.
At some point in the past or future.
- One day my prince will come.
In the open
- The agreement was signed in the open.
Keep your options open
When you keep your options open, you don’t commit yourself to something.
An outside chance
An outside chance is a remote possibility.
- We only have an outside chance of winning the match.