This is an emerging acronym in tech, which generally means “streaming to a dedicated device” without infrastructure beyond the Internet itself.
This means anything that goes around the established cable, satellite, and wireless providers can be considered “over-the-top.” This is mainly used in the context of streaming services and devices, like Disney+, AppleTV, etc.
Why I Looked It Up
I was in a client presentation where “OTT” appear in a graphic on a slide. The client asked what it meant. Embarrassingly, no one on the sales team knew (even though it was our slide deck).