A person who parleys or takes part in a conference.

? One who takes part in a conference or discussion; a disputant. Obsolete. rare.

One who trysts: (a) ‘a person who convenes others,‥fixing the time and place of meeting’ (Jamieson); (b) one who appoints to meet another; (c) one…

One who is conferred with, a member of a conference. (Originally U.S.)

One who contributes to a ‘symposium’ on some topic (symposium, n. 2).

A person who takes part in a round-table conference or discussion (see Round Table, n. 5).

The member of a congress (annual or periodic).

A (leading) member of a conference.

transferred and figurative. A mountain guide or porter; a guide; an official who makes the preparations for a summit conference.