(aka Winter Solstice or Mid-Winter; Modranicht "Mother Night"; Mean Geimredh; Yuletide; Alban Arthan)

The darkest part of the year, the "Dark of the Year".  This is the Winter Soltice.  This is the time we wait for the eventual triumph of the sun.
Yule is a holiday recognized by many neoPagan and Wiccan groups, though not all. For example, the original Gardnerian rituals had no place for a Solstice Ritual. I don't have a clue when the name began to be used by modern Pagans. It is one of the four "Lesser Sabbats".

Yule is pretty much pronounced just like it looks (although if you want to make a stab at a Scandinavian sound, it'll be more like "yool" and less like "yewl.")

The names Modranicht and Yule are Anglo-Saxon in origin.  Yule is purported to be from the Norse for "wheel", or Yula, Anglo-Saxon for "wheel".  In actuality, Jola (Iula in Old English) is the Norse term for December in general and the Twelve Days of Christmas in particular.  Some  elder etymologists have tried to link the term with "Hjol", an older Germanic term for "wheel", but the evidence is not compelling.  Jule is also a Norwegian meaning "to beat, thresh, whip", and Jula, a general Scandinavian term for a "yawl".