Explanation
Te-form of ～ぶる, meaning 'acting/pretending to be ~'.
Formation
Noun/Adjective + ぶる → ぶって (te-form)
Detailed explanation
～ぶる (in te-form: ～ぶって) indicates 'behaving as if one were ~.' This is often used negatively to criticize someone for putting on airs or pretending to know more than they do (e.g., 知ったかぶって 'to act like a know-it-all').
Examples
Kare wa nandemo shittaka butte hanashi o suru.
He talks as if he knows everything.
Kanojo wa nanimo shiranai furi o shite butte ita ga, hontou wa zenbu wakatte iru.
She was acting like she didn’t know anything, but in reality, she understands it all.
Kare wa itsumo erasou butte mawari ni sashizu shite iru.
He’s always bossing people around as if he’s so important.
Otona butte iru kedo, mada kodomoppoi tokoro ga aru.
He acts grown-up, but he still has some childish traits.
Practice
Grammar content sourced from hanabira.org.