The crossword solution for the term 'Prey for a Lion' is GNU, which is a three-letter acronym for 'GNU's Not Unix'. It is a free and open source software operating system that was created in 1983 by Richard Stallman. The GNU Project was launched to develop a complete Unix-like operating system which is free software—free as in freedom, not price. The GNU Project has been successful in creating a fully functional operating system, known as GNU/Linux, which is used by millions of people around the world.