The Collaborative International Dictionary of English v.0.48:

Coincident \Co*in"ci*dent\ (k[-o]*[i^]n"s[i^]*dent), a. [Cf. F.
   co["i]ncident.]
   Having coincidence; occupying the same place;
   contemporaneous; concurrent; -- followed by with.
   [1913 Webster]

         Christianity teaches nothing but what is perfectly
         suitable to, and coincident with, the ruling principles
         of a virtuous and well-inclined man.     --South.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Coincident \Co*in"ci*dent\, n.
   One of two or more coincident events; a coincidence. [R.]
   "Coincidents and accidents." --Froude.
   [1913 Webster]

WordNet (r) 3.0 (2006):

coincident
    adj 1: occurring or operating at the same time; "a series of
           coincident events" [syn: coincident, coincidental,
           coinciding, concurrent, co-occurrent,
           cooccurring, simultaneous]
    2: matching point for point; "coincident circles"

Moby Thesaurus II by Grady Ward, 1.0:

107 Moby Thesaurus words for "coincident":
   accessory, accompanying, accordant, affirmative, agreeable,
   agreeing, answerable, associate, associated, at one, at one with,
   attendant, attending, coacting, coactive, coadunate, coequal,
   coexistent, coexisting, coextensive, coherent, coincidental,
   coinciding, collaborative, collateral, collective, collusive,
   combined, combining, commensurate, compact, compatible,
   comprehensive, concerted, concomitant, concordant, concurrent,
   concurring, conformable, congenial, congruent, congruous, conjoint,
   conjugate, conjunct, consentaneous, consentient, consilient,
   consistent, consonant, conspiratorial, cooperant, cooperating,
   cooperative, coordinate, corporate, correlative, correspondent,
   corresponding, coterminous, coupled, coworking, en rapport, equal,
   equivalent, fellow, harmonious, in accord, in agreement,
   in rapport, in sync, in synchronization, inaccordance, inclusive,
   inharmony, joined, joint, like-minded, meeting, mutual, of a piece,
   of like mind, of one mind, on all fours, paired, parallel,
   parasitic, positive, proportionate, reconcilable, saprophytic,
   self-consistent, simultaneous, symbiotic, synchronized,
   synchronous, synergetic, synergic, synergistic, synonymous, twin,
   unanimous, uniform, unisonant, unisonous, united, uniting