Ar"sis (#), n. [L. arsis, Gr. a raising or lifting, an elevation of the voice, fr. to raise or apprehension; originally and properly it denotes the lifting of the hand in beating time, and hence the unaccented part of the rhythm.]
1. Pros. (a)
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. Hermann
That elevation of voice now called metrical accentuation, or the rhythmic accent.
⇒ It is uncertain whether the arsis originally consisted in a higher musical tone, greater volume, or longer duration of sound, or in all combined.
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.
© Webster 1913.