noun

• (grammar) The noun, pronoun or noun phrase about whom the statement is made. In active clauses with verbs denoting an action, the subject is the actor. In clauses in the passive voice the subject is the target of the action.
  "In the active sentence ‘The cat ate the mouse’, ‘the cat’ is the subject and ‘the mouse’ is the object."
• (music) The main theme or melody, especially in a fugue.
  "The earliest known form of subject is the ecclesiastical cantus firmus, or plain song."
• (philosophy) A being that has subjective experiences, subjective consciousness, or a relationship with another entity.
• (logic) That of which something is stated.

verb

• (transitive, construed with to) To cause (someone or something) to undergo a particular experience, especially one that is unpleasant or unwanted.
  "I came here to buy souvenirs, not to be subjected to a tirade of abuse!"
• (transitive) To make subordinate or subservient; to subdue or enslave.