1. She made us clean the hall.

2. We saw him dancing in the hall.

(What does 'hall' mean in each sentence, a building, a big room or a hallway?)

In the first sentence, it can mean any of those.

In the second sentence, it can mean any of those.

In each of the sentences you provided, the word "hall" can have a slightly different meaning depending on the context. Let me explain:

1. She made us clean the hall.
In this sentence, "hall" most likely refers to a big room or a large area within a building. It could be a community hall, an event hall, or any spacious room that requires cleaning.

2. We saw him dancing in the hall.
In this sentence, "hall" could refer to a hallway, which is a narrow passageway connecting rooms or different areas within a building. It typically does not have much space to dance. However, without further context, it could also mean a larger room used for recreational activities, such as a ballroom or an assembly hall.

To determine the precise meaning, it is essential to consider the overall context and the specific usage of the word "hall" within the given sentence.