adjective (a)

• bound or obligated, as under a pledge to a particular cause, action, or attitude(adj.all)

  Example:
  Committed church members.
  A committed Marxist.
  

  Antonym:
  uncommitted
  

  source: wordnet30
• associated in an exclusive sexual relationship(adj.all)

  Synonym:
  attached
  Antonym:
  unattached, uncommitted
  

  source: wordnet30