Etymology 1

Noun

1. A person who takes part in dialogue or conversation.
   • 1894, Calvin Thomas, "The Teacher's Outfit in German," The School Review, vol. 2, no. 7, p. 406,

     Explanations which continually remind one's interlocutor of one's ignorance are a great damper upon the easy flow of talk.

2. A man in the middle of the line in a minstrel show who questions the end men and acts as leader.
   • 1991, Maureen Costonis, "Martha Graham's American Document: A Minstrel Show in Modern Dance Dress," American Music, vol. 9, no. 3, p. 299,

     The "interlocutor" greeted the audience and engaged in comical repartee with the "end men," named Tambo and Bones.

Etymology 2

Noun

1. A decree of a court.
   • 1869, "The Judicial System of Scotland," The American Law Register (1852-1891), vol. 17, no. 5, p. 257,

     A decree of the English Court of Chancery is not entitled to more respect in Scotland than a decree (interlocutor) of the Scottish Court of Session in England.

Noun

1. negotiator