Oort cloud

Từ điển Oxford Learners Wordfinder Dictionary

noun

(astronomy) a hypothetical huge collection of comets orbiting the sun far beyond the orbit of Pluto;
perturbations (as by other stars) can upset a comet's orbit and may send it tumbling toward the sun
• Topics:
astronomy, uranology
• Hypernyms:
collection, aggregation, accumulation, assemblage