I know this is an old post, but I have a suggestion not yet mention.
As a pair
UnrepeatableTrigger
RepeatableTrigger
work well.
Though, much like Microsoft, when using the registry to ensure that things happen only once on startup, they use the term RunOnce.
So instantly, I would recognize
RunOnceTrigger
as being something more maintainable and clear than
OnceTrigger
OneShotTrigger
almost sounds desperate "we've only got one shot at this and if it fails we're up the creek without a paddle".
Monochronic and Polychronic
do not seem to be relevant, as mentioned here.
Monochronic and polychronic time
systems are two terms used to refer to
time and its influence on society.
monochronic time
system means that things are done one
at a time and time is segmented into
precise, small units.
Here are some other adjectives.. I particularly like Unrepeatable
just beause it sounds like you're talking about a family taboo, or Voldermort.
http://www.macmillandictionary.com/thesaurus-category/american/Happening-only-once