Full Idea
The axiomatic approach does not presuppose that truth can be defined. Instead, a formal language is expanded by a new primitive predicate of truth, and axioms for that predicate are then laid down.
Gist of Idea
Instead of a truth definition, add a primitive truth predicate, and axioms for how it works
Source
Volker Halbach (Axiomatic Theories of Truth (2005 ver) [2005], 1)
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.2
A Reaction
Idea 15647 explains why Halbach thinks the definition route is no good.
Related Idea
Idea 15647 Truth definitions don't produce a good theory, because they go beyond your current language [Halbach]