the person or thing that is worse than all others [↪ the best]
This year's harvest is the worst that people can remember.
Last year was by far the worst (=much worse than any other) for road accidents.
I think the worst is over now.
The worst of it is (=the worst part of the situation is), I can't tell anyone what's happening.
at its/his etc worst
You saw the garden at its worst, I'm afraid (=when it is worse than any other time).
most of something, or the most unpleasant or difficult part of it:
The worst of the storm seemed to be over.
to expect or fear that something will not be successful or something bad will happen:
When it got so late and they still weren't home, I began to fear the worst.
to lose a fight or argument
if things are as bad as they can be:
Choosing the right software can be time-consuming at best and confusing or frustrating at worst.
used to say that someone can try to harm you but they will not be able to:
They can do their worst now, because I'm leaving in three weeks.
7 especially British English, if worst comes to worst especially American English
if the situation develops in the worst possible way:
If the worst comes to the worst, we'll sell the car.