di·a·phone \ˈdīəˌfōn\noun (-s) Etymology:dia- + -phone 1.: all the variants of a phoneme that occur in all utterances of all speakers of a language < in French the tongue-trilled r used by some speakers and the uvula-trilled r used by other speakers belong to the same diaphone > 2.: a fog signal similar to a siren 3.: a powerful pipe-organ stop of peculiar construction of 8-foot, 16-foot, or 32-foot pitch