High German

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. German as indigenously spoken and written in Austria, Switzerland, and central and southern Germany.
2. n. The standard variety of German used as the official language in Germany and Austria and as one of the official languages in Switzerland.

Wiktionary

1. n. any of a group of West Germanic languages or dialects spoken in Switzerland, Austria and southern Germany, which is divided into the Central German group (including standard German as well as Luxembourgish, Pennsylvania German, and others) and the Upper German group (including Alemannic, Bavarian, and others)
2. n. the standard variety of the German language spoken and written in Germany, Austria and part of Switzerland, where it is also an official language.

GNU Webster's 1913

1. n. the Teutonic dialect of Upper or Southern Germany, -- comprising Old High German, used from the 8th to the 11th century; Middle H. G., from the 12th to the 15th century; and Modern or New H. G., the language of Luther's Bible version and of modern German literature. The dialects of Central Germany, the basis of the modern literary language, are often called Middle German, and the Southern German dialects Upper German; but High German is also used to cover both groups.
2. adj. See under German.

WordNet 3.0

1. n. the standard German language; developed historically from West Germanic