Union type

Data type that allows for values that are one of multiple different data types

In computer science, a union is a value that may have any of multiple representations or formats within the same area of memory; that consists of a variable that may hold such a data structure. Some programming languages support a union type for such a data type. In other words, a union type specifies the permitted types that may be stored in its instances, e.g., float and integer. In contrast with a record, which could be defined to contain both a float and an integer; a union would hold only one at a time.

This keyword could refer to multiple things. Here are some suggestions: