An expression in the usage of a language that is peculiar to itself either in having a meaning that cannot be derived from the conjoined meanings of its elements or in its grammatically atypical use of words.
do or die
to make a great effort
It was do or die for the man when he started his new job.
List of common idioms, their meanings and examples of their usage in sentences
An idiom is defined as - a group of words whose meaning is different from the meanings of the individual words.