Wiktionary
thioesterase
n. (context organic compound English) Any of various enzymes of the esterase family that exhibit esterase activity specifically at a thiol group.
Wikipedia
Thioesterase
Thioesterases are enzymes which belong to the esterase family. Esterases, in turn, are one type of the several hydrolases known.
Thioesterases exhibit Esterase activity (splitting of an ester into acid and alcohol, in the presence of water) specifically at a thiol group.
Thioesterases or thiolester hydrolases are identified as members of E.C.3.1.2.