The spelling of the word "zestocausis" can be quite challenging at first glance, but its pronunciation is straightforward when understood with IPA Phonetics. The two syllables in "zesto-" can be pronounced as "zest-oh" with a short "e" sound followed by a long "o" sound. The "-cau" syllable sounds like "cause" with a soft "s" sound. The final "-sis" syllable is pronounced as "sis" with a short "i" sound. Altogether, the word is pronounced as "ZEST-oh-kaws-sis."
Cauterization by means of hot steam.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.