Idioms starting with O/P

On the ball

To be aware of and understand what is happening and be able to react quickly

On everyone's lips

If something is on everyone’s lips, they are all talking about it

On the horizon

Likely to happen soon

Once bitten, twice shy

After an unpleasant experience you are careful to avoid something similar

Out of your hands

No longer your responsibility

Out of the blue

Unexpectedly, without warning

Out of hand

Difficult or impossible to control

Out of the frying pan into the fire

From a bad situation to one that is worse

On the nose

Something that is exact or precise

Once in a blue moon

Very rarely