Definition of digraphs:
(n) :
(linguistics) A pair of letters, especially a pair representing a single phoneme.
(n) :
(graph theory) A directed graph.
(n) :
(computing) A two-character sequence used to enter a single conceptual character.
(n) :
(divination of the Taixuanjing) a sequence of two lines, each of which may be unbroken, broken once, or broken twice.