Genuinely curious question: how does something come to be defined as cutting edge? Is it more of a feeling when someone is working on something that just seems

Genuinely curious question: how does something come to be defined as cutting edge? Is it more of a feeling when someone is working on something that just seems so far away from the norm? Is everyone who is researching ways to cure cancer on the cutting edge, or is it a very small subset of that group? Is it defined by how close someone is to actually achieving a discovery?