A "pTLD" stands for pseudo Top-Level Domains. According to the definition I found in Wikipedia, these include .bitnet, .csnet, .exit, .i2p, .local, .onion, .oz, .freene and .uucp and have no meaning in the global Domain Name System.
A blog about New gTLDs and dotBrands (.BRANDs) from the ICANN new gTLD program. You can subscribe to The gTLD Club's Newsletter.