Find the word definition

Wiktionary
inverted breve

n. A diacritical mark whose appearance is of a breve upside-down, thus similar to a rounded circumflex.

Wikipedia
Inverted breve

Inverted breve or arch is a diacritical mark, shaped like the top half of a circle , that is, like an upside-down breve . It looks similar to the circumflex , but the circumflex has a sharp tip; the inverted breve is rounded: compare  â Ê ê Î î Ô ô Û û (circumflex) with Ȃ ȃ Ȇ ȇ Ȋ ȋ Ȏ ȏ Ȗ ȗ (inverted breve).

Inverted breve can occur above or below the letter. It is not used in any natural language alphabet, but only as a phonetic indicator though it is identical in form to the Ancient Greek circumflex.