Sometimes also abbreviated as “2LD”. This term is commonly used to describe domain extensions where the Top Level Domain (TLD) is not available, good examples are “.CO.NZ” and “.CO.UK”. For many years these two extensions only allowed registrations under the Second Level Domain “CO”.
The domain “octopoly.CO.NZ” is actually a Third Level Domain with “octopoly” being the third level and “CO” the Second Level. Most extensions allow the registration of domain names directly under their TLD. We were able to register our name also under the .NZ TLD, octopoly.nz.