9 letters · 12 points in Scrabble
noun any substance used to slow down neutrons in nuclear reactors
noun in the Presbyterian church, the officer who presides over a synod or general assembly
noun someone who presides over a forum or debate
originLearned borrowing from Latin moderātor. First attested as Middle English moderatour. By surface analysis, moderate + -or.
Etymology from Wiktionary, CC BY-SA 3.0