Pronunciation: \'[macron over o]-v[schwa]r-,s[macron over i]t\
1 : the act or duty of overseeing : watchful care <He was assigned oversight of the project.>
2 : an error or something forgotten through carelessness or haste <It was surely an oversight that you weren't invited.>
Headscratcher: What do "watchful care" and "careless error" have in common? Though they are opposites they are both meanings of oversight.