In hematology, "syneresis" means "clot retraction".
syneresis, synaeresis [s'nərss]
1 (Chem) the process in which a gel contracts on standing and exudes liquid, as in the separation of whey in cheese-making

2 the contraction of two vowels into a diphthong

3 another word for: synizesis
[ETYMOLOGY: 16th Century: via Late Latin from Greek sunairesis a shortening, from sunairein to draw together, from syn- + hairein to take]

In poetry, it means something else:
A type of elision in which two contiguous vowels within a word which are normally pronounced as two syllables, as in seest, are pronounced as one syllable instead.