Mansion n. : A dwelling place, -- whether a part or whole of a house or other shelter.

Mansion n. : The house of the lord of a manor; a manor house; hence: Any house of considerable size or pretension.

Mansion n. : A twelfth part of the heavens; a house. See 1st House, 8.

Mansion n. : The place in the heavens occupied each day by the moon in its monthly revolution.

Mansion v. i. : To dwell; to reside.

Example:
When is a house considered a Mansion?

Taxonomy
mansion, Spanish Mansion, century mansions, the 19th century, estates, Samuel McIntire, Twenty-eight mansions, England, free encyclopedia, 19th century, Latin America, country home, gardens, manor, large estates, Estancia, Europe, architectural styles.

Defination from the web:
mansion was defined as a house which contained a ballroom and tens of bedrooms. ... territorial holdings granted to a lord who would remain there — hence it can be seen how the word 'Mansion' came to have its meaning. ... A mansion near Almelo, The Netherlands ...