Arsis

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.

2.

That elevation of voice now called metrical accentuation, or the rhythmic accent.

3.

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.