Pronunciation: (pros-thē'sis for 1; pros'thu-sis for 2),[key] —n., —pl.-sesPronunciation: (-sēz for 1; -sēz" for 2).[key] 1. a device, either external or implanted, that substitutes for or supplements a missing or defective part of the body.
2. Gram.,Prosody.the addition of one or more sounds or syllables to a word or line of verse, esp. at the beginning.