Is handshake an ATS?

Excuse me, could you clarify something for me? I've come across the term "handshake" in the context of cryptocurrency and finance, but I'm unsure if it's being used as an abbreviation for an Alternative Trading System, or ATS. Is handshake, in this particular context, referring to an ATS, or is it being used in a different sense entirely? I'd appreciate any insight you could offer to help me better understand this terminology.