That name the hobbits only knew in legends of the dark past, like a shadow in the background of their memories; but it was ominous and disquieting.
The tidings were mostly sad and ominous: of gathering darkness, the wars of Men, and the flight of the Elves.
The sound was ominous.
They began to feel that all this country was unreal, and that they were stumbling through an ominous dream that led to no awakening.
So it went on, until his forties were running out, and his fiftieth birthday was drawing near: fifty was a number that he felt was somehow significant (or ominous); it was at any rate at that age that adventure had suddenly befallen Bilbo.
They had been in fear of pursuit for so long that any sound from behind seemed ominous and unfriendly.
The dark patches grew darker, but they shrank; and suddenly he saw, towering ominous before him and leaning slightly towards one another like the pillars of a headless door, two huge standing stones.
Beyond the ominous water were reared vast cliffs, their stern faces pallid in the fading light: final and impassable.
Now dark and ominous it loomed up in the night.
Tall and sheer and ominous they stood upon either side of the stream.
There are no more uses of "ominous" in the book.
Show samples from other sources
I’m beginning to hear ominous rumblings of discontent.
With the clouds looking so ominous, I’m afraid there will be a bad storm.