The Collaborative International Dictionary of English v.0.48:

Coterminous \Co*ter"mi*nous\ (k?-t?r"m?-n?s), a. [Cf.
   Conterminous.]
   Bordering; conterminous; -- followed by with.
   [1913 Webster]

WordNet (r) 3.0 (2006):

coterminous
    adj 1: being of equal extent or scope or duration [syn:
           coextensive, coterminous, conterminous]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "coterminous":
   accompanying, adjacent, adjoining, agreeing, bordering, coequal,
   coetaneous, coeternal, coeval, coexistent, coexisting, coextensive,
   coincident, coincidental, coinciding, coinstantaneous, collateral,
   concomitant, concurrent, congruent, connecting, contemporaneous,
   contemporary, conterminous, contiguous, correspondent,
   corresponding, end to end, endways, endwise, equal, equivalent,
   face to face, immediate, isochronal, isochronous, joined,
   juxtaposed, juxtapositional, juxtapositive, neighbor, neighboring,
   next, simultaneous, synonymous, unison, unisonous