Dictionary / Vocabulary / タメ口をきく
タメぐちをきく
to talk casually; to use one's peer language (to others)
Also written タメ口を聞く、ため口をきく、ため口を聞く
最近は、年下のくせにため口を聞く奴が多すぎる。
These days more and more young people talk to their elders on even terms.