Full Idea
We could think of a referring expression in Fregean terms as what he calls a proper name (Eigenname): its Sinn (sense) is supposed to determine an object as opposed to a concept as its Bedeutung (referent).
Gist of Idea
A Fregean proper name has a sense determining an object, instead of a concept
Source
report of Gottlob Frege (On Sense and Reference [1892]) by Mark Sainsbury - The Essence of Reference 18.1
Book Reference
'Oxford Handbook of Philosophy of Language', ed/tr. Lepore,E/Smith,B [OUP 2008], p.395
A Reaction
The problem would be that the same expression could precisely indicate an object on one occasion, nearly do so on another, and totally fail on a third.