From The Collaborative International Dictionary of English v.0.48 [gcide]:
umlaut \um"laut\ ([=oo]m"lout), noun [G., from um about + laut sound.] (Philol.) The euphonic modification of a root vowel sound by the influence of a, u, or especially i, in the syllable which formerly followed.
Note: It is peculiar to the Teutonic languages, and was common in Anglo-Saxon. In German the umlauted vowels resulting from a, o, u, followed by old i, are written [aum], ["o], ["u], or ae, oe, ue; as, m[aum]nner or maenner, men, from mann, man. Examples of forms resulting from umlaut in English are geese pl. of goose, men pl. of man, etc.
From WordNet (r) 3.0 (2006) [wn]:
The dictionary definitions are retrieved from a local copy of two of the open source DICT dictionaries. Click here for the database copyright information. DEFINE.COM is registered as an educational NONPROFIT corporation. We aim to please around here. We believe in using positive reinforcement to get things done. We make suggestions that are intended to make life more enjoyable. We think about efficiency, automation, security, PRIVACY, social and ecological responsibility and positive HUMANITARIAN ethics and VALUES. We are benevolent. DO NO HARM is our motto.