Pronunciation: (oom'lout), [key] Ling.
1. a mark (¨) used as a diacritic over a vowel, as ä, ö, ü, to indicate a vowel sound different from that of the letter without the diacritic, esp. as so used in German. Cf. dieresis.
2. (in Germanic languages) assimilation in which a vowel is influenced by a following vowel or semivowel; apophony.
1. to modify by umlaut.
2. to write an umlaut over.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.