Full Idea
A definition of a word is correct if the definition can be substituted for the word being defined in an assertion without in the least changing the meaning which the assertion is felt to have.
Gist of Idea
A correct definition is what can be substituted without loss of meaning
Source
Curt Ducasse (Nature and Observability of Causal Relations [1926], §1)
Book Reference
'Causation', ed/tr. Sosa,E. /Tooley,M. [OUP 1993], p.125
A Reaction
This sounds good, but a very bland and uninformative rephrasing would fit this account, without offering anything very helpful. The word 'this' could be substituted for a lot of object words. A 'blade' is 'a thing always attached to a knife handle'.