Definition of "Chair" :
noun: the position of professor
"He was awarded an endowed chair in economics."
noun: a seat for one person, with a support for the back
"He put his coat over the back of the chair and sat down."
noun: a particular seat in an orchestra
"He is second chair violin."
noun: an instrument of execution by electrocution; resembles an ordinary seat for one person
"The murderer was sentenced to die in the chair."
noun: the officer who presides at the meetings of an organization
"Address your remarks to the chairperson."
verb: preside over
verb: act or preside as chair, as of an academic department in a university
"She chaired the department for many years."