Hate speech is language intended to cause harm against a particular individual or group, often based on their racial, ethnic, religious, or gender identity. Hate speech is widespread on social media, and is increasingly common in mainstream political discourse. That said, there is no clear consensus as to what constitutes hate speech. In addition, human moderators come with their own biases, and automatic computer algorithms are often easy to fool. All of these factors complicate the efforts of social media platforms to filter or reduce such content. During this interactive workshop we will discuss examples from Twitter in the hopes of reaching some consensus as to what is and is not hate speech. We will also try to determine what kind of knowledge a human moderator or an automatic algorithm would need to have in order to make this determination. We will try to avoid particularly graphic examples of hate speech and focus on more subtle cases.