The Collaborative International Dictionary of English v.0.48:

Roundabout \Round"a*bout`\, n.
   1. A large horizontal wheel or frame, commonly with wooden
      horses, etc., on which children ride; a merry-go-round; a
      carousel. [British] --Smart.
      [1913 Webster +PJC]

   2. A dance performed in a circle. --Goldsmith.
      [1913 Webster]

   3. A short, close jacket worn by boys, sailors, etc.
      [1913 Webster]

   4. A state or scene of constant change, or of recurring labor
      and vicissitude. --Cowper.
      [1913 Webster]

   5. a traffic circle. [Chiefly British]
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Roundabout \Round"a*bout`\, a.
   1. Circuitous; going round; indirect; as, roundabout speech.
      [1913 Webster]

            We have taken a terrible roundabout road. --Burke.
      [1913 Webster]

   2. Encircling; enveloping; comprehensive. "Large, sound,
      roundabout sense." --Locke.
      [1913 Webster]

WordNet (r) 3.0 (2006):

roundabout
    adj 1: marked by obliqueness or indirection in speech or
           conduct; "the explanation was circuitous and puzzling";
           "a roundabout paragraph"; "hear in a roundabout way that
           her ex-husband was marrying her best friend" [syn:
           circuitous, roundabout]
    2: deviating from a straight course; "a scenic but devious
       route"; "a long and circuitous journey by train and boat"; "a
       roundabout route avoided rush-hour traffic" [syn: devious,
       circuitous, roundabout]
    n 1: a road junction at which traffic streams circularly around
         a central island; "the accident blocked all traffic at the
         rotary" [syn: traffic circle, circle, rotary,
         roundabout]
    2: a large, rotating machine with seats for children to ride or
       amusement [syn: carousel, carrousel, merry-go-round,
       roundabout, whirligig]

Moby Thesaurus II by Grady Ward, 1.0:

181 Moby Thesaurus words for "roundabout":
   Byzantine, Ferris wheel, O-shaped, ambages, ambagious, ambient,
   anfractuous, apparent, backhanded, balled up, bypass, carousel,
   chubby, chute-the-chutes, chutes, circling, circuit, circuitous,
   circular, circumambages, circumambient, circumbendibus,
   circumferential, circumflex, circumfluent, circumfluous,
   circumjacent, circumlocution, circumlocutional, circumlocutory,
   collateral, complex, complicated, confounded, confused, convoluted,
   convolutional, cortical, crabbed, daedal, detour, deviating,
   deviation, deviative, devious, digression, digressive, discursive,
   disk, elaborate, embracing, embrangled, encircling, enclosing,
   encompassing, enfolding, entangled, enveloping, environing,
   epidermic, evasive, excursion, excursive, exomorphic, exterior,
   external, extrinsic, flexuose, flexuous, flying horses, fouled up,
   fringe, helical, implicated, indirect, intricate, involute,
   involuted, involutional, involved, jaunt, junket, knotted,
   labyrinthian, labyrinthine, long, loused up, many-faceted, matted,
   mazy, meandering, meandrous, merry-go-round, messed up, mixed up,
   mucked up, multifarious, neighboring, oblique, open, orbital, out,
   out-of-the-way, outer, outermost, outing, outlying, outmost,
   outside, outstanding, outward, outward-facing, peripheral,
   periphrase, periphrasis, periphrastic, perplexed, pleonasm, plump,
   podgy, public, pudgy, ramified, redundancy, rivose, rivulose,
   roller, roller coaster, rolling stone, roly-poly, rotary, rotator,
   rotor, round, round trip, roundabout way, ruffled, runaround,
   rundle, sally, screwed up, seeming, seesaw, serpentine, sinuate,
   sinuose, sinuous, snaky, snarled, spiral, subtle, suburban,
   superficial, surface, surrounding, swing, tangled, tangly,
   tautology, teeter-totter, top, torsional, tortile, tortuous,
   traffic circle, tubby, turning, twisted, twisting, twisty,
   verbality, wheel, whip, whirlabout, whirler, whirligig, whorled,
   winding, wrapping, wreathlike, wreathy