To me a lightworker is someone who works for the greater good of humanity. Someone who works to bring the world into the light, and teaches people, sharing their knowledge while as gaining new knowledge at the same time.
Here are some web definitions
•A person driven and motivated to do work which makes the world a better place, improves peoples' lives, and/or elevates people to a higher level
en.wiktionary.org/wiki/lightworker
•lightworkers - are those who seek the truth on their spiritual journey toward Enlightenment. They feel the urge to heal others and a deep need to resolve the issues of the world.
www.amorillum.com/page3.htm