Any stock that is NOT an NMS (National Market System) stock under FINRA is an "OTC Equity Security, i.e., non-NMS stocks such as OTCBB securities, Pink Sheets securities, ADRs, Canadian issues, foreign securities, non-exchange listed DPP securities, and Restricted Equity Securities."
FINRA Rule series 6620 and 7300 apply to this group, "OTC Equity Securities."