When it comes to business partnerships, it's not uncommon for the involvement of one partner to remain hidden or unknown. This is where the term "silent partner" comes in. However, there are several other phrases that could be used to describe this type of arrangement. A "sleeping partner" refers to someone who has invested in a business but has no active involvement in its operations. An "inactive partner" is similar to a silent partner, but may still have some involvement in decision making. A "backer," "financier," or "angel investor" are also synonymous with silent partner, as they provide funding for a business without actively participating in day-to-day operations.