Especially Law. A person who conducts a thorough search.
Origin
Mid 17th century; earliest use found in Thomas Blount (1618–1679), antiquary and lexicographer. From classical Latin perquīsītor person who conducts a thorough search, in post-classical Latin also person who acquires, buyer, purchaser from perquīsīt-, past participial stem of perquīrere + -or.