Today, searching for the term "cloak", I came across these definitions
From Longman DOCE 5th Ed.
cloak noun [singular] an organization, activity, or way of behaving that deliberately protects someone or keeps something secret
From Oxford Advanced Learners Dictionary 8th Ed.
cloak noun singular (literary) a thing that hides or covers sb/sth
I really expected to see "uncountable" rather than "singular" for this meaning. What difference between the two noun types that I am missing?