Full Idea
Today we expect that anything worth calling a definition should imply a semantics.
Gist of Idea
A decent modern definition should always imply a semantics
Source
Ian Hacking (What is Logic? [1979], §10)
Book Reference
'A Philosophical Companion to First-Order Logic', ed/tr. Hughes,R.I.G. [Hackett 1993], p.239
A Reaction
He compares this with Gentzen 1935, who was attempting purely syntactic definitions of the logical connectives.