"signal" is a pretty word for a "pump group".
a couple of years ago the pump groups were very popular. we even had a couple of topics here on bitcointalk. I believe one of them was called "ryan pumper". but eventually people figured out that these things were big scams so they stopped giving their money to them willingly.
that meant they had to change their ways. so they started masking the fact that they are pump groups and started using things like "signal groups" as a way to get the same old attention and abuse the fact that this market is filled with newcomers who have no idea what to do and need someone to take their hands and walk them through things.