A "wave signal" refers to a pattern of energy that travels through space or a medium. It is a way for information or data to be transmitted, similar to how radio or Wi-Fi signals work. Full definition
The merging black holes generated a gravitational wave signal from 1.3 billion light - years away — but which direction did they come from? (space.com)
The ultimate dream of mine would be to detect the gravitational wave signal of a neutron - neutron star merger. (kavlifoundation.org)
The radio wave signals emitted by e.g. the hot plasma surrounding the black hole are recorded separately at the individual telescopes. (blackholecam.org)