1 lesser, smaller, secondary, subordinate, subsidiary:
The minor planets are bodies orbiting the sun in the asteroid belt
2 insignificant, obscure, inconsequential, unimportant, trifling, trivial, negligible, inconsiderable, slight, petty, paltry, small, Colloq small-time, one-horse, Brit two a penny, US minor-league, bush-league, penny-ante, two-bit, picayune:
It is a minor matter to me whether you stay or go. She is only a minor player in this game.
3 child, youngster, youth, stripling, teenager, adolescent, schoolboy, schoolgirl, boy, girl, lad, laddie, lass, lassie, Law ward, infant:
At your age, you are still a minor in the eyes of the law.