/sin'euh zee"sis/ , n. Phonet.
the combination into one syllable of two vowels (or of a vowel and a diphthong) that do not form a diphthong. Also called synaeresis .
[ 1840-50; synízesis, equiv. to syn- SYN- + ( h ) iz- (s. of hízein to SIT 1 ) + -esis -ESIS ]