High-risk refers to the possibility of harm or damage that is likely to occur in a particular situation. There are several synonyms for high-risk that can be used interchangeably based on the context. Some of these synonyms include dangerous, precarious, uncertain, speculative, hazardous, and precarious. All these terms describe something that is risky and has the potential to cause harm or loss. High-risk scenarios include investing in a startup, driving on a dangerous road, or gambling. It's important to be aware of the potential risks involved in any situation, and to consider all the available alternatives before making a decision.