ಅರ್ಥ : Any substance used to slow down neutrons in nuclear reactors.
ಅರ್ಥ : In the Presbyterian church, the officer who presides over a synod or general assembly.
ಅರ್ಥ : Someone who presides over a forum or debate.
ಅರ್ಥ : Someone who mediates disputes and attempts to avoid violence.