a mark (ˇ) used over certain consonant letters in the orthography of some languages to indicate a specific sound, or used in certain systems of symbols for representing speech sounds
See haček in American Heritage Dictionary 4
(häˈchĕkˌ)
noun
A diacritical mark (˘) that resembles an inverted circumflex and is used over certain letters, such as č, to indicate quality of pronunciation.