means To loom is to appear large, dim, and threatening, often gradually emerging into view — or, as a noun, the machine that weaves thread into cloth.

from Two different words wearing one spelling. The weaving 'loom' comes from Old English 'gelōma,' meaning a tool or utensil — so a loom is literally just 'the implement.' The verb 'loom,' meaning to appear menacingly, is murkier: it surfaces around the 16th century, possibly tied to a Low German or Scandinavian word for slow movement, and was first used of ships emerging hugely out of sea-mist before it spread to anything that rises up and threatens.