1. without logical or meaningful connection; disjointed; rambling: an incoherent sentence.
2. characterized by such thought or language, as a person: incoherent with rage.
3. not coherent or cohering: an incoherent mixture.
4. lacking physical cohesion; loose: incoherent dust.
5. lacking unity or harmony of elements: an incoherent public.
6. lacking congruity of parts; uncoordinated.
7. different or incompatible by nature, as things.
8. Physics. (of a wave) having a low degree of coherence.