An all-too-common sentence: “I am nauseous.”
The issue: The perversion of meaning by substitution of a different word. Something nauseous is something that makes one sick. “I am nauseated.” is probably what was meant.
This happens with other expressions as well. e.g. “You have another thing coming.” for “You have another think coming. ” (You should rethink your position.) “having free reign” for “having free rein”. (The expression comes from a horse having free rein.)