Full Idea
A 'quasi-quotation' [corner quotes, Quine quotes] designates that (unspecified) expression which is obtained from the contents of the corners by replacing the Greek letters by the (unspecified) expressions which they designate.
Clarification
Corner quotes are written like the top left- and right- corners of a square (not in this font!)
Gist of Idea
'Corner quotes' (quasi-quotation) designate 'whatever these terms designate'
Source
Willard Quine (Mathematical Logic (revised) [1940], 1.6)
Book Reference
Quine,Willard: 'Mathematical Logic (revised)' [Harvard 1979], p.36
A Reaction
Filed under 'variables', as they seem to be variables that can refer to actual expressions, like algebra. Quine was determined to distinguish clearly between 'mention' and 'use'. 'Half-hearted substitutional quantification', says Fine.