Meaning of “junior” - Learner’s Dictionary

junior

adjective uk us /ˈdʒuːniər/
LOW RANK

B2 low or lower in rank:

a junior minister/senator
YOUNG PEOPLE

B2 for or relating to young people:

NAME (written abbreviation Jr) mainly US

used at the end of a man's name to show that he is the younger of two men in the same family who have the same name:

Hello, I'd like to speak to Mr Anderson, Junior.

(Definition of “junior adjective” from the Cambridge Learner’s Dictionary © Cambridge University Press)