'Digram' definitions:

Definition of 'digram'

From: WordNet
noun
Two successive letters (especially two letters used to represent a single sound: `sh' in `shoe') [syn: digraph, digram]

Definition of 'Digram'

From: GCIDE
  • Digram \Di"gram\, n. [Gr. di- = di`s- twice + ? letter.] A digraph. [1913 Webster]