The word "aposia" is a rare term used in medical contexts, referring to the inability to appreciate certain sensations. The word starts with the vowel sound /ə/, as in "uh". The next syllable features the vowel sound /oʊ/, as in "go". The third syllable has a sound similar to the "sh" in "ship", represented as /ʃə/. The last syllable is pronounced with an /iə/ sound, as in "ear". Therefore, the correct pronunciation would be "uh-POH-shuh-eer". Proper understanding of IPA phonetic transcription can help to avoid confusion and improve communication.
Absence of the feeling of thirst.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.