Lewis & Short

† thĕsis, is, f., = θέσις, in rhetoric,

  1. I. a proposition, thesis (pure Lat. propositum), Quint. 3, 5, 11; 3, 5, 14; 2, 4, 24; 7, 10, 5; 12, 2, 25; Sen. Contr. prooem.
  2. II. In prosody, the falling of the voice, the thesis (opp. arsis), Mart. Cap. 9, §§ 974 and 985.