What is "nimber"

n. Any of a set of number-like objects, also called the Grundy numbers, used in :w:combinatorial game theory.

In mathematics, the nimbers, also called Grundy numbers, are introduced in combinatorial game theory, where they are defined as the values of nim heaps. They arise in a much larger class of games because of the Sprague–Grundy theorem. The nimbers are the ordinal numbers endowed with a new nimber addition and nimber multiplication, which are distinct from ordinal addition and ordinal multiplication. The minimum excludant operation is applied to sets of nimbers.