EDIT Synonyms double pipe,

 siri  eki 

EDIT - Khoisan tradition - "x" in Zulu orthography

 siri  eki 

EDIT Linguistics In the international Phonetic Alphabet (IPA): alveolar lateral click. It is a sound that is found in some South African languages. The sound is created by quickly moving the side of the tongue away from the row of teeth, it is like the click that's used to hurry up a horse.

 eki  jsw