WordWeb Online

1. The subject of a sentence that expresses the actual agent of an expressed or implied action (as father in "it is your father speaking") or that is the thing about which something is otherwise predicated (as to do right in "it is sometimes hard to do right").
   "The notion of a logical subject can be made more precise in terms of a definition of reference, for something is a logical subject only if it is a referent of a sentence token."

Type of: subject