The main definition of the term planet would be "a world dominating it's own orbit around a star" where the term "world" would include only naturally spherical astronomical objects (the term should be more exactly defined by specialists in astronomical evolution, I'm merely a philosopher).
Such things as rogue planets (planets recently broken away from their systems) or planets orbiting star-like objects (not actual stars) etc. are all semantically derivative (important words always have more than one meaning), and don't affect this definition.