moderator

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. One that moderates, as:
2. n. One that arbitrates or mediates.
3. n. One who presides over a meeting, forum, or debate.
4. n. The officer who presides over a synod or general assembly of the Presbyterian Church.
5. n. Physics A substance, such as water or graphite, that is used in a nuclear reactor to decrease the speed of fast neutrons and increase the likelihood of fission.

Century Dictionary and Cyclopedia

1. n. One who or that which moderates, restrains, or represses.
2. n. In microscopy, a device used to diminish the intensity or vary the character of the light which illuminates the object: it consists commonly of a screen of opal glass, ground glass, or glass of a pale-blue or neutral tint.
3. n. An umpire; a judge.
4. n. The person who presides at a meeting or disputation: now used chiefly in churches of the Presbyterian and Congregational order (as, the moderator of a presbytery or of the General Assembly), and in town-meetings in the United States.
5. n. In the universities of Cambridge and Oxford, one of the public officers appointed to superintend the examinations for honors and degrees: so called because they formerly had to moderate or preside in the exercises of undergraduates for the degree of bachelor of arts.
6. n. A moderator-lamp.
7. n. In astrology, any one of the four principal points in a nativity upon which the native's fortunes are supposed to depend: the sun, moon, ascendant, or mid-heaven.
8. n. In mech., a device for moderating or reducing the speed of an internal-combustion engine by the operation of a throttle-valve. Its action is the reverse of that of the accelerator.

Wiktionary

1. n. someone who moderates
2. n. the person who presides over a synod of a Presbyterian Church
3. n. physics a substance (often water or graphite) used to decrease the speed of fast neutrons in a nuclear reactor and hence increase likelihood of fission
4. n. a device used to deaden some of the noise from a firearm, although not to the same extent as a suppressor or silencer.
5. n. UK An examiner at Oxford and Cambridge universities.
6. n. Ireland At the University of Dublin, either the first (senior) or second (junior) in rank in an examination for the degree of Bachelor of Arts.
7. n. A mechanical arrangement for regulating motion in a machine, or producing equality of effect.

GNU Webster's 1913

1. n. One who, or that which, moderates, restrains, or pacifies.
2. n. The officer who presides over an assembly or discussion to preserve order, propose questions, regulate the proceedings, and declare the votes.
3. n. In the University of Oxford, an examiner for moderations; at Cambridge, the superintendant of examinations for degrees; at Dublin, either the first (senior) or second (junior) in rank in an examination for the degree of Bachelor of Arts.
4. n. A mechanical arrangement for regulating motion in a machine, or producing equality of effect.

WordNet 3.0

1. n. someone who mediates disputes and attempts to avoid violence
2. n. any substance used to slow down neutrons in nuclear reactors
3. n. in the Presbyterian church, the officer who presides over a synod or general assembly
4. n. someone who presides over a forum or debate