This is the 194th most frequent Russian word.
большой
Big.
'Большой' is used here as an adjective to describe the size of the house.
Это большой дом.
This is a big house.
In this sentence, 'большой' conveys the idea of a significant or extensive amount of experience.
У него большой опыт работы.
He has extensive work experience.
Here, 'большой' is used figuratively to denote an important or substantial advancement.