Meaning Two: Disappointing, Unpleasant, Overdone.
Meaning Three: A testimony made by a clam.
Originally it was verbal only, pronounced unexpectedly by a text to speech program.
Eventually out of necessity it was given a non verbal spelling and since then it's popularity has risen considerably from a buzz word to an intricate part of everyday language.
While at first some were confused as to it's nature (being inherently contradictory) it's meaning is more often than not determined by context, and failing that, attributed to sarcasm.
"Wow. Today has been such a clamstimony day."