C2 adjective /pɔːrˈtɛntəs/
portentous
前兆的な、重大な
Meaning
Giving a sign or warning that something, often bad or serious, is going to happen; or overly solemn and pompous.
Example
His portentous tone made everyone nervous about the news.
彼の前兆的な口調は、ニュースについて皆を不安にさせた。