appear as a vague or shadowy form, especially one that is large or threatening

vehicles loomed out of the darkness

(of an event) seemingly about to happen and regarded as ominous or worrying

the looming threat of social unrest

the government has not woken up to the looming crisis

appearing as a vague or shadowy form, especially one that is large or threatening

he almost expected to see Jason's looming figure suddenly appear

she walked beneath the looming battlements of Balvenie Castle