|Definition - A speech impairment that causes you to lose control of intonation and rhythm.|
Etymology - The word was coined by combining the prefix dys, bad or abnormal, with the word prosody, which derives from the Greek prosoidia, song sung to music (from pros, to + oide, song or poem). Thus, etymology-wise, the term (sort of) means "bad singing."
Oxford English Dictionary - Its first citation is from 1947:
"(heading) Dysprosody, or altered ‘Melody of Language’."
(G. H. Monrad-Krohn in Brain LXX. 405)