It can also function as a verb, as in "He is bullying the smaller kids." But in the question, "What part of speech is the word bullying?", it is being used as a noun, referring to the act of bullying itself.
It can also function as a verb, as in "He is bullying the smaller kids." But in the question, "What part of speech is the word bullying?", it is being used as a noun, referring to the act of bullying itself.