I. ˈüm-ˌlau̇t, ˈu̇m- noun
Etymology: German, from um- around, transforming + Laut sound
Date: circa 1845
1.
a. : the change of a vowel (as ü to ē in goose, geese ) that is caused by partial assimilation to a succeeding sound or that occurs as a reflex of the former presence of a succeeding sound which has been lost or altered
b. : a vowel resulting from such partial assimilation
2. : a diacritical mark ¨ placed over a vowel to indicate a more central or front articulation — compare diaeresis
II. transitive verb
Date: 1879
1. : to produce by umlaut
2. : to write or print an umlaut over