Synonyms of 'flippancy'
frivolityDictionary, cheek (informal) , irreverence
His flippancy subsided rapidly.
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If someone talks or behaves in a rather impolite and disrespectful way, you can call this behaviour impertinence or an impertinence.
The impertinence of the boy is phenomenal!
chutzpah (US , Canadian , informal)
brass neck (British , informal)
His irreverence for authority marks him out as a troublemaker.
Thesaurus for flippancy from the Collins English Thesaurus
the quality or state of being flippant