This is the 7112th most frequent Russian word.
большие
"Big" or "large" (plural form).
In this sentence, 'большие' is used as an adjective describing the noun 'деревья', indicating their significant size.
У нас в саду растут большие деревья.
We have large trees growing in our garden.
Here, 'большие' is an adjective describing the noun 'неприятности', emphasizing the seriousness or magnitude of the troubles.
Большие неприятности начались, когда он забыл документы.
Big troubles started when he forgot the documents.
In this usage, 'большие' acts as an adjective describing the noun 'города', referring to cities of considerable size or population.