not expressed or organized clearly, and therefore difficult to understand:
an incoherent, over-long action movie
He called the policy 'incoherent and ill-thought out'.
speaking in a way that cannot be understood, because you are drunk, feeling a strong emotion etc:
Ben, drunk and incoherent, slumped in a chair.
She began to mutter incoherently.
—incoherence noun [uncountable]