Adjective
Consisting of one letter only; as, a uniliteral word or sign.
Source: Webster's dictionaryDue to the fact that the phonetic realization of Egyptian cannot be known with certainty, Egyptologists use a system of transliteration to denote each sound which could be represented by a uniliteral hieroglyph. Source: Internet
Phonograms formed with one consonant are called uniliteral signs; with two consonants, biliteral signs; with three triliteral signs. Source: Internet