This is the 44th most frequent Indonesian word.
besar
Big; large.
In this sentence, 'besar' means 'big' and is used as an adjective to describe the size of the house.
Rumah itu sangat besar.
That house is very big.
In this case, 'besar' is used to describe the magnitude of the loss, meaning 'significant.'
Perusahaan tersebut mengalami kerugian besar tahun ini.
The company suffered a significant loss this year.
Here, 'besar' indicates 'great' or 'significant,' applied metaphorically to describe the level of influence.