The Collaborative International Dictionary of English v.0.48:

Ancestral \An*ces"tral\ (?; 277), a.
   Of, pertaining to, derived from, or possessed by, an ancestor
   or ancestors; as, an ancestral estate. "Ancestral trees."
   --Hemans.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ancestral
    adj 1: inherited or inheritable by established rules (usually
           legal rules) of descent; "ancestral home"; "ancestral
           lore"; "hereditary monarchy"; "patrimonial estate";
           "transmissible tradition" [syn: ancestral,
           hereditary, patrimonial, transmissible]
    2: of or belonging to or inherited from an ancestor

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "ancestral":
   aboriginal, ancestorial, antepatriarchal, atavistic, autochthonous,
   fatherlike, fatherly, grandfatherly, grandmotherly, grandparental,
   humanoid, maternal, mother, motherlike, motherly, parent, parental,
   paternal, patriarchal, preadamite, preglacial, prehistoric,
   prehuman, prime, primeval, primitive, primogenial, primoprimitive,
   primordial, pristine, protohistoric, protohuman



Bouvier's Law Dictionary, Revised 6th Ed (1856):

ANCESTRAL. What relates to or has, been done by one's ancestors; as homage
ancestral, and the like.