As a noun it is a machine on which we turn thread to cloth
As a verb I can say that if something looms or looms up (from somewhere, out of something), you can feel it either through your sight (eyes) or ears or even through you mind.
* As the day of my interview loomed, I became increasingly nervous. Here you feel the approaching interview through your mind.
* When we turned at the fork, a giant bear loomed in front of us. Here you see something which has suddenly appeared in front of you (sight)
And here are some words which are commonly used with Loom as a verb:
Skyscraper: having existed the airport, skyscrapers of N.Y loomed from everywhere
She started to walk faster when a dark shadow loomed from her behind.
Disaster, crisis, cloud, ......