Full Idea
An 'implicit definition' characterizes a structure or class of structures by giving a direct description of the relations that hold among the places of the structure.
Gist of Idea
An 'implicit definition' gives a direct description of the relations of an entity
Source
Stewart Shapiro (Philosophy of Mathematics [1997], Intro)
Book Reference
Shapiro,Stewart: 'Philosophy of Mathematics:structure and ontology' [OUP 1997], p.13
A Reaction
This might also be thought of as a 'functional definition', since it seems to say what the structure or entity does, rather than give the intrinsic characteristics that make its relations and actions possible.