TRIGRAPH
Source: 567
Tri″graph (?), n. [[Pref. tri- + -graph.]] Three letters united in pronunciation so as to have but one sound, or to form but one syllable, as -ieu in adieu; a triphthong.
Source: 567
Tri″graph (?), n. [[Pref. tri- + -graph.]] Three letters united in pronunciation so as to have but one sound, or to form but one syllable, as -ieu in adieu; a triphthong.