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."