Source : Webster's Revised Unabridged Dictionary (1913)

Insession \In*ses"sion\, n. [L. insessio, fr. insidere,
   insessum, to sit in. See {Insidious}.]
   1. The act of sitting, as in a tub or bath. ``Used by way of
      fomentation, insession, or bath.'' [R.] --Holland.

   2. That in which one sits, as a bathing tub. [R.]

            Insessions be bathing tubs half full. --Holland.