[ee-th
er-awr, ahy-ther-] 
| allowing no equivocation; being limited in choice to two options: It's an either-or situation—you pay the bill or you lose the company's services. |
| ei·ther-or (ē'thər-ôr', ī'thər-) n. A strictly limited choice or division between only two options. adj. Of or characterized by a choice or division limited strictly between two options: found ourselves in an either-or situation. |