What does "voidable" mean?

Voidable: (Law) Capable of being avoided, or of being adjudged void, invalid, and of no force; capable of being either avoided or confirmed. If the metropolitan . . . grants letters of administration, such administration is not, but voidable by sentence. Ayliffe. Note: A voidable contract may be ratified and confirmed; to render it null and of no effect, it must be avoided; a void contract can not be ratified.