And/or

"Objectionable to many, who regard it as a legalism," says Roy H. Copperud in A Dictionary of Usage and Style. Either say and or say or.

Occasionally this solution does not work, as in this sentence: "When cake is cool, top with whipped cream and/or chopped nuts." In such cases, try x or y or both: "When cake is cool, top with whipped cream or chopped nuts or both."