What is another word for in a building?
Pronunciation: [ɪn ɐ bˈɪldɪŋ] (IPA) 
When referring to a location, the phrase "in a building" can be substituted for various synonyms. For example, one could say "in a structure," "indoors," or "within a edifice." Other options include "inside a facility," "inside a construction," or "within a complex." Depending on the context, "in a construction" or "inside a establishment" may also be appropriate. Additionally, one could use the phrase "within four walls" or "under a roof" to convey a sense of being in a confined space. Ultimately, the choice of synonym will depend on the desired tone and level of formality.
