Lewis & Short

sessor, ōris, m. [sedeo], one who sits in a place, a sitter (not ante-Aug. and very rare).

  1. I. In gen., a sitter in the theatre, Hor. Ep. 2, 2, 130.
      1. 2. A sitter upon a horse, a horseman, rider, Sen. Const. 12 fin.; Suet. Caes. 61; Veg. 2, 28, 34.
  2. * II. In partic., one who tarries or dwells in a place, an inhabitant, resident: sessores veteres urbis, Nep. Cim. 2, 5.