From down +‎ bow.

• IPA^(key): /ˈdaʊnbəʊ/

downbow (plural downbows)

1. (music) A note performed on a string instrument by drawing the bow downward or to the right across the instrument, moving its point of contact from the frog toward the tip of the bow.

downbow (third-person singular simple present downbows, present participle downbowing, simple past and past participle downbowed)

1. (geology) To curve or arc downwards.
   • 1997, A. E. M. Nairn, A. S. Alsharhan, Sedimentary Basins and Petroleum Geology of the Middle East:

     Slumps and sediment gravity flow could signify steepening of the slope resulting from tectonic downbowing of the continental margin.

• bow down