lets the cat out of the bag (verb) spill: reveal
Sinonime: adventitious,
casual,
chance,
coincidental,
contingent, fluky, fortuitous,
inadvertent,
incidental, random, uncalculated, unexpected,
unforeseen, unintended, unintentional,
unplannedAntonime: decided, designed,
essential,
intended,
intentional, planned, premeditated