The Collaborative International Dictionary of English v.0.48:

Detour \De`tour"\, n. [F. d['e]tour, fr. d['e]tourner to turn
   aside; pref. d['e]- (L. dis-) + tourner to turn. See Turn.]
   A turning; a circuitous route; a deviation from a direct
   course; as, the detours of the Mississippi.
   [1913 Webster]

WordNet (r) 3.0 (2006):

detour
    n 1: a roundabout road (especially one that is used temporarily
         while a main route is blocked) [syn: detour, roundabout
         way]
    v 1: travel via a detour

Moby Thesaurus II by Grady Ward, 1.0:

96 Moby Thesaurus words for "detour":
   aberrancy, aberration, ambages, back door, back road, back stairs,
   back street, back way, bear off, bend, bias, branch off,
   branching off, by-lane, bypass, bypath, byroad, bystreet, byway,
   change the bearing, circuit, circuitousness, circumbendibus,
   circumnavigate, circumvent, corner, crook, curve, declination,
   depart from, departure, deviance, deviancy, deviate, deviation,
   deviousness, digress, digression, discursion, divagate, divagation,
   divaricate, divarication, diverge, divergence, diversion, divert,
   dogleg, double, drift, drifting, errantry, excursion, excursus,
   exorbitation, go around, go round about, hairpin, heel,
   indirection, make a detour, obliquity, pererration, rambling,
   roundabout, roundabout way, runaround, sheer, shift, shifting,
   shifting course, shifting path, side door, side road, side street,
   skew, slant, straying, sweep, swerve, swerving, swinging, tack,
   trend, turn, turn aside, turn away from, turning, twist, variation,
   vary, veer, wandering, warp, yaw, zigzag