The Collaborative International Dictionary of English v.0.48:

Predecessor \Pred`e*ces"sor\ (?; 277), n. [L. praedecessor; prae
   before + decessor one who withdraws from the province he has
   governed, a retiring officer (with reference to his
   successor), a predecessor, fr. decedere: cf. F.
   pr['e]d['e]cesseur. See Decease.]
   One who precedes; one who has preceded another in any state,
   position, office, etc.; one whom another follows or comes
   after, in any office or position.
   [1913 Webster]

         A prince who was as watchful as his predecessor had
         been over the interests of the state.    --Prescott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

predecessor
    n 1: one who precedes you in time (as in holding a position or
         office)
    2: something that precedes and indicates the approach of
       something or someone [syn: harbinger, forerunner,
       predecessor, herald, precursor]

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "predecessor":
   ancestor, ancestors, announcer, antecedent, antecedents,
   ascendants, avant-garde, bellwether, buccinator, bushwhacker,
   elders, explorer, fathers, forebear, forebears, forefather,
   forefathers, foregoer, forerunner, front runner, frontiersman,
   fugleman, grandfathers, grandparents, groundbreaker, guide,
   harbinger, herald, innovator, lead runner, leader, messenger,
   pathfinder, patriarchs, pioneer, point, precedent, precursor,
   predecessor, predecessors, progenitors, prototype, scout,
   stormy petrel, trailblazer, trailbreaker, vanguard, vaunt-courier,
   voortrekker



The Free On-line Dictionary of Computing (30 December 2018):

parent
mother
predecessor

    The ancestor node in a tree that
   points to the current node (one of its child nodes).

   (2005-09-15)


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

PREDECESSOR. One who has preceded another.
     2. This term is applied in particular to corporators who are now no
longer such, and whose rights have been vested in their successor; the word
ancestor is more usually applicable to common persons. The predecessor in a
corporation stands in the same relation to the successor, that the ancestor
does to the heir.
     3. The term predecessor is also used to designate one who has filled an
office or station before the present incumbent.