A disjunctive sequence is an infinite sequence (over a finite alphabet of characters) in which every finite string appears as a substring. For instance, the binary Champernowne sequence
0
1
00
01
10
11
000
001
…
{\displaystyle 0\ 1\ 00\ 01\ 10\ 11\ 000\ 001\ldots }
formed by concatenating all binary strings in shortlex order, clearly contains all the binary strings and so is disjunctive. (The spaces above are not significant...