Ichidan verb, Transitive verb
to fix upon (one-sidedly); to (ignore someone's position and) arbitrarily decide something is the case
そういうの、先入観っていうんだよっ!体験したこと無いのに、決め付けるのはよくないっ!That's what they call 'prejudice'! It's wrong to make your mind up on something you've never experienced! to scold; to take (a person) to task
Also written 決めつける【きめつける】