Idioms are phrases which cannot be understood simply by looking at the meaning of the individual words in the phrase.
crack a smile
to let a smile show on one`s face
Our boss never cracked a smile during the meeting.
List of common idioms, their meanings and examples of their usage in sentences
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.