Typically, a Single Purpose Entity (SPE in conventional jargon) is an LLC used for one purpose only. SPE's are also referred to as a single-asset or special purpose entity.  They are a legal entity created to satisfy a narrow, specific or temporary purpose. SPE's are typically used to isolate liability between companies and among other assets.

I teach real estate investors to put each piece of real estate they buy in a single Land Trust. Therefore, each Land Trust is a SPE. For those of my students (especially in California) that have trouble with title companies, closing agents and attorneys (who have mental issues with the words, "Land Trust.") I would suggest they start using the terminology "SPE". In other words, from the beginning of your conversation with these closing actors, do not say you are using a "Land Trust." Tell, them you are using a "Single Purpose Trust." Or, you could also refer to them as "Single Purpose Business Entities." It really does not matter what you call them, what is in the Trust Agreement controls the players.