From BiblePortal Wikipedia

Webster's Dictionary [1]

(1): ( n.) A continuous narrative arranged from the first four books of the New Testament.

(2): ( n.) The interval of a fourth.

(3): ( n.) An electuary compounded of four medicines.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [2]

in Biblical literature, a harmony of the four Gospels. (See Harmony); (See Tatian).