A zygodrome is a positive integer whose maximal runs of equal digits in its ordinary decimal representation all have length at least two. Thus 11, 100, 1122, and 777000 are zygodromes, while 101 and 1123 are not. Equivalently, every digit has an equal neighboring digit within its maximal run.
The name is recreational terminology and depends on base 10. The same definition can be applied in another base by requiring every run in the corresponding positional representation to have length at least two.
