Webster's Revised Unabridged Dictionary · 1913

Demonstrator

Demonstrator (?; 277) , noun

[Latin: compare French démonstrateur.]

1.
One who demonstrates;
(a)
one who proves anything with certainty, or establishes it by indubitable evidence.
(b)
one who shows how a certain device operates or a procedure is performed.
2.
(Anatomy) A teacher of practical anatomy.
3.
a person who participates in a demonstration{7}.