NNN is an abbreviation for "triple net lease," which is a type of commercial lease structure in real estate. In a triple net lease, the lessee is responsible for covering certain costs associated with operating the property in addition to paying their base rent. These operating expenses tend to fall into three separate categories, or "nets," which are real estate taxes, property insurance, and operating expenses. Triple net leases are commonly found in commercial real estate and tend to have lower rents because the tenant assumes ongoing expenses that would otherwise be the responsibility of the property owner. Other types of net leases include single net leases, in which the tenant pays property taxes, and double net leases, which include property taxes and property insurance. It is important to clarify the parking aspect upfront when considering a triple net lease.

It is worth noting that "NNN" can also refer to "No Nut November," which is a challenge where a person attempts to go the whole month of November without ejaculating.