To ridicule, make fun of, or look down on someone — to treat someone as a fool or belittle them.
人を馬鹿にするのはよくない。
It's not good to make fun of people.
彼女は自分の意見を馬鹿にされたと感じた。
She felt that her opinion had been ridiculed.
上司に馬鹿にされて怒りが込み上げた。
I got angry when my boss made fun of me.