What does 'portentous' specifically imply about an event?

The term 'portentous' specifically conveys a sense of foreboding, suggesting that an event carries significant weight or importance, often implying that it heralds something ominous or menacing. When something is described as portentous, it is not merely noteworthy; it typically indicates that what is about to happen is not only serious but may also suggest danger or an impending consequence. This connotation of foreboding is key to understanding the use of the word in various contexts, often serving as a precursor to a significant, and sometimes troubling, change.

In this context, the other options do not align with this meaning. Predictability does not necessarily incorporate the gravity or ominous nature associated with portentous events. Similarly, describing something as trivial contradicts the weight implied by the term, while celebratory connotations would not fit with the seriousness associated with portentous occurrences. Therefore, recognizing 'portentous' as conveying foreboding captures the essence of its use in language.