The buttocks or more specifically, the anus.

A stupid, mean or despicable person.

To be silly, act stupid or mess around.

"Stop arsing around!"

The stronger part of a musical measure: the part containing the beat.

The stronger part of a metrical foot: the part containing the long (heavy) syllable in quantitative meter, or the stressed syllable in a qualitative meter.

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 the thesis.

The elevation of the voice to a higher pitch in speaking.