either-or rule
nounUK /ˈaɪðər ɔː ruːl/
US /ˈiːðər ɔːr ruːl/
A rule that says you must pick one of two choices, not both.
The game follows an either-or rule: you can be the seeker or the hider, but not both.
RELATED WORDS
OTHER MEANINGS
2. In logic, a rule stating that exactly one of two statements must be true.
The either-or rule means the light is either on or off, never both.
3. A situation where only two outcomes are possible.
For the field trip, it's an either-or rule: bring a packed lunch or buy one at the café.
4. A guideline that forbids combining two alternatives at the same time.
The club's either-or rule says you can join the chess team or the art club, not both.