Intestate describes an estate where the person died without a valid will, so state law, rather than instructions the person left behind, determines who inherits and in what shares. Tennessee's intestate succession statute sets that order, and it gives real property to the heirs at law immediately at death.
Why it matters
Dying intestate means state law, not a document, decides who has to agree to sell the house.
In Tennessee: Tenn. Code Ann. § 31-2-103. This can work differently in another state.
General information, not legal or tax advice.