https://www.cnet.com/news/harvard-scientists-suggest-strange-asteroid-could-be-a-probe-from-an-alien-civilisation/

Oumuamua is interesting for a number of reasons. First and foremost, it's the first interstellar asteroid of its time ever seen by humans. Secondly, it's an odd shape, being flat and elongated. Thirdly, and perhaps most importantly, it moves strangely. As per the paper, it shows "deviations from a Keplerian orbit at a high statistical significance". In short: It doesn't move like a regular comet or asteroid.

The paper attempts to explain that strange movement and comes up with a number of possible scenarios. The first: solar radiation pressure.