Arsis

1. n. 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.
2. n. 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.
3. n. That elevation of voice now called metrical accentuation, or the rhythmic accent.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.