资料来源 : pyDict

自明之理,陈词滥调,众所周知,老生常谈

资料来源 : Webster's Revised Unabridged Dictionary (1913)

Truism \Tru"ism\, n. [From {True}.]
   An undoubted or self-evident truth; a statement which is
   pliantly true; a proposition needing no proof or argument; --
   opposed to falsism.

         Trifling truisms clothed in great, swelling words. --J.
                                                  P. Smith.

资料来源 : WordNet®

truism
     n : an obvious truth