lacking the ability to express oneself, esp. in clear and effective speech

an inarticulate public speaker.

unable to use articulate speech

inarticulate with rage.

not articulate; not uttered or emitted with expressive or intelligible modulations

His mouth stuffed, he could utter only inarticulate sounds.

not fully expressed or expressible

a voice choked with inarticulate agony.

Anatomy, Zoology . not jointed; having no articulation or joint.