Binary Decimal Meaning

(informal) Used other than as an idiom: A decimal (numeral written as a concatenation of successive negative powers of the base) in base 2..

Example: 1938, G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, section 9.7:
  Any positive integer up to inclusive can be expressed uniquely as a binary decimal of figures, i.e., as a sum , where every is or .