Lewis & Short

interjectĭo, ōnis, f. [interjacio], a throwing or placing between, insertion.

  1. I. In gen.: verborum, Auct. Her. 1, 6, 9.
  2. II. In partic.
    1. A. In gram., an interjection, Quint. 1, 4, 19.
    2. B. In rhet., a parenthesis, an interruption of the principal idea by the insertion of another: interjectio qua et oratores et historici frequentes utuntur, ut medio sermone aliquem inserant sensum, Quint. 8, 2, 15.