adj. Used to describe word roots in Semitic languages which consist of four letters
n. A word root in a Semitic language which consists of four letters
the GNU version of the Collaborative International Dictionary of English
adj. Consisting of four letters.
The Century Dictionary and Cyclopedia
Consisting of four letters, or of only four constant letters or consonants.
n. A word or a root consisting of four letters or containing four consonants.
Word Usage
"All other feet, primary or secondary, consist necessarily of seven letters, as they contain a triliteral Watad (see supra i. 2) with either two biliteral Sabab khafíf (i. 1) or a quadriliteral Fásilah"