Definition of "uncharacteristically"

This newfound infatuation renders Bart uncharacteristically vulnerable. He suddenly has something to care about beyond causing trouble and makes a dramatic transformation from hell-raiser to gentleman about town.

2012 May 27, Nathan Rabin, “TV: Review: THE SIMPSONS (CLASSIC): “New Kid On The Block” (season 4, episode 8; originally aired 11/12/1992)”, in The Onion AV Club‎