(informal) Any one of the four Slavic languages (viz. Czech, Serbo-Croatian, Slovak, and Slovene) and two Baltic languages (viz. Latvian and Lithuanian) that use the háček (ˇ) for the letters Č, Š, and Ž (more, depending on the language) as part of their standard orthographies.
English Wiktionary. Available under CC-BY-SA license.