Nonrealizable

The term repetition, as applied tp an event of nature, is clearly ideal and nonrealizable in any concrete case, like the term equality and the term circle. No two concrete objects in nature ever ideally equal in every respect.

Source: wiktionary

This method appears promissing for on-line identification, and it appears to be emminently satisfactory for off-line use, where physically nonrealizable filter characteristics can be simulated to permit identification rates which approach the maximum.

Source: wiktionary

It should be clear that the parallel structure makes the function nonrealizable, since it is not possible to pass a plane through an n-cube which will dichotomize the function.

Source: wiktionary