For automotive technicians the term unmeasured is know as unmetered. Unmetered is not a term recognized by the English language dictionary yet.

Unmetered air leaks are any air entering the engine without being metered by sensors.   The 02 or oxygen sensor will detect the air leak by setting a lean code.  One common leak is the intake manifold to engine mounting gaskets.   Other causes are vacuum hoses, air intake tubing, throttle body shaft wear, PCV system, and cracks in plastic manifolds.   These unmetered air leaks can cause engine performance issues such as rough idle, stumble, and hesitation.