WordNet sense 1 (an assistant subject to the authority or control of another):

subsidiary, underling, foot soldier

WordNet sense 2 (a word that is more specific than a given word):

hyponym, subordinate word

WordNet sense 3 (compliant and obedient to authority):

subservient

WordNet sense 4 (being under the power or sovereignty of another or others):

dependent, subject, subject

WordNet sense 5 (inferior in rank or status):

inferior, lowly, petty, subaltern, junior-grade, lower-ranking

WordNet sense 6 (younger; lower in rank; shorter in length of tenure or service):

junior

WordNet sense 7 (lower in rank, power, or authority):

under

WordNet sense 8 (belonging to a lower class or rank):

secondary

WordNet sense 9 (of or relating to a person who is subordinate to another):

assistant

WordNet sense 10 (lower in rank or importance):

low-level

WordNet sense 11 (make subordinate, dependent, or subservient):

subdue