What is "thioester"

n. (context organic chemistry English) Any of several classes of organic compound in which one or both oxygen atoms of an ester group are replaced by those of sulfur

Thioesters are compounds with the functional group C–S–CO–C. They are the product of esterification between a carboxylic acid and a thiol. Thioesters are widespread in biochemistry, the best-known derivative being acetyl-CoA.