Full Idea
Almost everyone agrees that intelligible definite descriptions may lack a referent; this has historically been a reason for not counting them among referring expressions.
Gist of Idea
Definite descriptions may not be referring expressions, since they can fail to refer
Source
Mark Sainsbury (The Essence of Reference [2006], 18.2)
Book Reference
'Oxford Handbook of Philosophy of Language', ed/tr. Lepore,E/Smith,B [OUP 2008], p.398
A Reaction
One might compare indexicals such as 'I', which may be incapable of failing to refer when spoken. However 'look at that!' frequently fails to communicate reference.