Words meaning to cancel or make ineffective are void, revoke, annul, counteract, offset, invalidate...
Two options are overturn and repeal.
it is sensation
stops and quits, but its more 4 letter word than 5, i just added plural and also abort
cancel
bail out
feckless
It is ineffectual (not inaffectual), and it means ineffective.
Forceless or Failing
cancel
If you mean "ineffective", that means it's not effective.
revoke! :)
enactive. noun of enact Having power to establish a law.
Exit Stop Close Discontinue
Repeal
it means bad cast.. as in The Indian caste system
The word "cancel" is the opposite of sit, in the sense of convene.
Circumstances = situation.Considering the circumstances, I think I will cancel my flight.