catflap.org Online Dictionary Query

  without rhyme or reason /wɪðˌaʊt ɹˈaɪm ɔː ɹˈiːzən/
  ohne Hand und Fuß [übtr.]
   see: hand, hands, by hand, manual, manually, shake hands, firsthand, secondhand, buy secondhand, at hand, link hands, give sb. (a) free rein, find sth. easy, sb. finds sth. easy, with sure touch, She is all (fingers and) thumbs when it comes to baking., She can't bake her way out of a paper bag., She can't bake for toffee.
  

  without rhyme or reason /wɪðˌaʊt ɹˈaɪm ɔː ɹˈiːzən/
  ohne System, ganz unsystematisch, ohne roten Faden 
   see: The articles bounce around from topic to topic, with no rhyme or reason., There is no rhyme or reason to this division.
  

  54 Moby Thesaurus words for "without rhyme or reason":
     absonant, aimless, arbitrarily, capriciously, contradictory,
     contrary to reason, designless, empty, fallacious, fancifully,
     faulty, flawed, flightily, garbled, illogical, importless, inane,
     inauthentic, inconclusive, incongruous, inconsequent,
     inconsequential, inconsistent, insignificant, invalid, irrational,
     lightly, loose, meaningless, nonconnotative, nondenotative,
     nonscientific, not following, null, paralogical, phatic,
     purportless, purposeless, reasonless, scrambled, self-annulling,
     self-contradictory, self-refuting, senseless, unauthentic,
     unconnected, unmeaning, unphilosophical, unreasonable,
     unreasonably, unscientific, unsignificant, whimsically,
     without reason
  
  

     无缘无故地,毫无道理地,莫名其妙地