Arsis /(är"sĭs)/

Ar·sis

Arsis

n.
  1. That part of a foot where the ictus is put, or which is distinguished from the rest (known as the thesis) of the foot by a greater stress of voice. (Pros.)
  2. The elevation of the hand, or that part of the bar at which it is raised, in beating time; the weak or unaccented part of the bar; -- opposed to thesis. (Mus.)