inarticulate
in-ar-tic-u-late
adjective
Unable to express ideas or feelings clearly or fluently through speech.
"He was often inarticulate when nervous."
Thesaurus
Synonyms: unarticulated, aphonic, aphasic, dumb, tongueless, unspoken, silent, wordless, unarticulate, tongue-tied, voiceless, speechless
Antonyms: articulate