In the context of an entire presumed talk, conference, interview, panel, or whatever presumably about race and racism... nah not really lol. Dude only really has about a minute to respond, and he probably spent already at least 30-45 minutes about it. At some point if I ask a biologist after a discussion about biology what a biologist is, "a biologist studies biology" makes sense. If you go to an entire talk/convo/conference/whatever about a subject and still need someone to define the subject to you, idk man?
With all the respect that is possible on an anonymous forum like Hacker News but I think you are wrong to not be concerned about a person receiving millions in donation funding (1) to counter racism who defines racism using the same word. It's a serious red flag and with the benefit of hindsight if you read the NY times article linked below there was and is very good reason to be concerned.
The person who asked the question states that he listened to the talk and did not hear any definition of racism. This is why he asked the question. If you're really curious you can listen to the whole talk (2). Not that I would recommend listening to the whole thing.