Definition of "háček"
háček
/ˈhɑːt͡ʃɛk/
noun
plural háčeks or háčky
(orthography and typography) A caron; a diacritical mark (ˇ) usually resembling an inverted circumflex, but in the cases of ď, Ľ, ľ, and ť resembling a prime (′) instead.
Quotations
Another orthographic practice […] was developed […] in the twentieth century: this is the adoption of the hacek for the representation of the Cypriot postalveolar fricatives and affricates, which are otherwise not distinguished by the normal characters of the Greek alphabet alone. It was not until very recently, therefore, that the spellings <σ̌>, <τσ̌>, <ζ̌> and <τζ̌>, for [ʃ], [tʃ], [ʒ] and [dʒ] respectively, became available.
2005, Stavroula Varella, Language Contact and the Lexicon in the History of Cypriot Greek, page 46