A family of Microsoft word processing software products for creating web, email, and print documents.
My approach to the requirement for exempting specific words in a given document is to create a "No Proofing" character style defined as Default Paragraph Font + Do not check spelling or grammar. Apply that to any words you don't want marked as errors.
I found this very helpful when I was working on a client's novel that used a lot of street slang and colloquialisms.