(they) started being pretentious

Translations
они стали вести себя претенциозно
они начали напускать на себя важность
они стали выпендриваться
они начали жеманничать
Definitions
They began to behave in an affected and self-important way.
They began trying to appear more important, sophisticated, or cultured than they really were.
Words
they

pronoun
они
started

verb
начали
being

verb
быть
pretentious

adjective
претенциозными