Oxford Advanced American Dictionary

Definition of worst noun from the Oxford Advanced Learner's Dictionary

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worst

noun
worst pronunciation English wɜːst worst pronunciation American wɜːrst
 
the worst [singular] the most serious or unpleasant thing that could happen; the part, situation, possibility, etc. that is worse than any otherThe worst of the storm was over.When they did not hear from her, they feared the worst.The worst of it is that I can't even be sure if they received my letter.He was always optimistic, even when things were at their worst.
Idioms

at (the) worst

used for saying what is the worst thing that can happen
At the very worst, he'll have to pay a fine.At worst this may mean the end of her playing career.

bring out the worst in somebody

to make somebody show their worst qualities
Pressure can bring out the worst in people.

do your worst

(of a person) to do as much damage or be as unpleasant as possibleLet them do their worst—we'll fight them every inch of the way.

get the worst of it

to be defeated
He'd been in a fight and had obviously got the worst of it.

if the worst comes to the worst

(North American English also if worst comes to worst) if the situation becomes too difficult or dangerousIf the worst comes to the worst, we'll just have to sell the house.

the worst of all (possible) worlds

all the disadvantages of every situation