nauseous, nauseated, nauseating
Using nauseous for nauseated is incorrect but so common that we can no longer call it an error.
But careful writers observe traditional meaning. The word nauseous describes something that causes nausea. The word nauseated relates to experiencing nausea. Here’s the rule:
Whatever is nauseous makes one feel nauseated. The word nauseating is commonly substituted for nauseous.
Example: I became nauseated after several nauseating (or nauseous) rides at the amusement park.