3 Terms and definitions [intro.defs]

3.64[defns.valid]valid but unspecified state

⟨library⟩ value of an object that is not specified except that the object's invariants are met and operations on the object behave as specified for its type
[Example 1: 
If an object x of type std​::​vector<int> is in a valid but unspecified state, x.empty() can be called unconditionally, and x.front() can be called only if x.empty() returns false.
— end example]