The Collaborative International Dictionary of English v.0.48:

Subjoinder \Sub*join"der\, n.
   An additional remark. [R.]
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "subjoinder":
   Parthian shot, address, affirmation, allegation, answer,
   apostrophe, assertion, averment, comment, crack, declaration,
   dictum, exclamation, expression, greeting, interjection, mention,
   note, observation, phrase, position, pronouncement, question,
   reflection, remark, say, saying, sentence, statement, thought,
   utterance, word