portentous

adj

1. Of momentous or ominous significance.

   “Well may it sort [be fitting] that this portentous figure comes armed through our watch, so like the King that was and is the question of these wars.”

   “It is no longer in my possession, but my memory holds almost every word of its portentous message; and again I affirm my confidence in the sanity of the man who wrote it.”

   “The chaplain's first mention of the name Yossarian! had tolled deep in his memory like a portentous gong.”

   “If the siege of Boston seemed to end in anticlimax, with the sudden retreat of British military forces, the siege of New York City seen from the inside, from under siege, seemed infinitely more portentous: “The Day is Come that in all Probility on which Depends the Salvation of this Countery.””

   “The main problem with To Believe, however, is that by combining two of their previous styles, the Cinematic Orchestra have landed on a sound that has become ubiquitous in the years they’ve been away – portentous, restrained and impeccably tasteful electronica.”

2. Ominously prophetic.
3. Puffed up with vanity.