tristate

adj

1. (not-comparable)Having, or pertaining to, three distinct states.

   “This tristate logic deals with true, false, and unknown values.”

2. (not-comparable)Of, pertaining to, or characteristic of a region in the United States where three state borders come to a single point.

   “The event will be sponsored by several tristate businesses.”

noun

1. A variable, etc. that can take any of three distinct values.

   “The 4 input ports are simply tristates that can be addressed to enable the data from any one of them to be read by the standard input port of the printer interface.”

   “Configuration options that control the build process are either Booleans or tristates.”

2. (capitalized, often)The area in some regions of the United States where three state borders come to a single point.

   “The Tristate is on alert after a rash of home burglaries.”