What is the meaning of ضمة?

an embracing

a number of horses assembled from every quarter for a race

damma, ḍamma, the diacritic in the Arabic script that represents the vowel /u/, appearing as a small curl placed above a letter:  ـُ

a hug

damma, the diacritic in the Arabic script that represents the vowel /u/, appearing as a small curl placed above a letter:  ـُ

Source: wiktionary.org