1. umlaut - Noun
2. umlaut - Verb
The euphonic modification of a root vowel sound by the influence of a, u, or especially i, in the syllable which formerly followed.
Source: Webster's dictionaryThe umlaut isn't on my birth certificate. I had this book as a child called Chloe and Maude, and there was an umlaut on the e, and I said, I want that! It's a little flair. Just to confuse people even more. Chloë Sevigny
As in Swedish and Estonian, these are regarded as individual letters, rather than vowel + umlaut combinations (as happens in German). Source: Internet
Compare Old English ġiest "guest", which shows umlaut, and Old High German gast, which does not, both from Proto-Germanic *gastiz. Source: Internet
Consequently, these dialects also make grammatical use of umlaut to form plurals and diminutives, much as most other modern Germanic languages do. Source: Internet
Because of the grammatical importance of such pairs, the German umlaut diacritic was developed, making the phenomenon very visible. Source: Internet
Also, from German, is über, which means "over" or "above"; it usually appears as a prefix attached to adjectives, and is frequently written without the umlaut over the u. Van de Velde & Meuleman. Source: Internet