To transliterate is to rewrite a word written in the letters of one alphabet (e.g., the Greek, Roman, Cyrillic, or Arabic alphabet) in the corresponding letters of another alphabet. Thus the Greek word φιλία (friendship) is transliterated in the Roman alphabet as 'philia' and the Russian word перестройка (reconstruction, reorganisation) as 'perestroika', while the English word 'computer' is transliterated into Arabic as ﻛﻤﺒﻴﻮﺗﺮ ('kumbutir').
The noun 'transliteration' may refer either to the act of transliterating - as in 'Transliteration is not always a straightforward matter' - or to what has been transliterated - as in 'Mimesis is a transliteration of the ancient Greek word μίμησις'.
The word 'transliterate' comes from the Latin littera (a letter of the alphabet) and the prefix 'trans-' (across, through, beyond).
Do not confuse 'transliterate' and 'translate' or 'transliteration' and 'translation'.