The Collaborative International Dictionary of English v.0.48:

Sewer \Sew"er\, n.
   1. One who sews, or stitches.
      [1913 Webster]

   2. (Zool.) A small tortricid moth whose larva sews together
      the edges of a leaf by means of silk; as, the apple-leaf
      sewer (Phoxopteris nubeculana)
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sewer \Sew"er\, n. [OF. sewiere, seuwiere, ultimately fr. L. ex
   out + a derivative of aqua water; cf. OF. essevour a drain,
   essever, esseuwer, essiaver, to cause to flow, to drain, to
   flow, LL. exaquatorium a channel through which water runs
   off. Cf. Ewer, Aquarium.]
   A drain or passage to carry off water and filth under ground;
   a subterraneous channel, particularly in cities.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sewer \Sew"er\, n. [Cf. OE. assewer, and asseour, OF. asseour,
   F. asseoir to seat, to set, L. assidere to sit by; ad +
   sedere to sit (cf. Sit); or cf. OE. sew pottage, sauce,
   boiled meat, AS. se['a]w juice, Skr. su to press out.]
   Formerly, an upper servant, or household officer, who set on
   and removed the dishes at a feast, and who also brought water
   for the hands of the guests.
   [1913 Webster]

         Then the sewer
         Poured water from a great and golden ewer,
         That from their hands to a silver caldron ran.
                                                  --Chapman.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sewer
    n 1: a waste pipe that carries away sewage or surface water
         [syn: sewer, sewerage, cloaca]
    2: someone who sews; "a sewer of fine gowns"
    3: misfortune resulting in lost effort or money; "his career was
       in the gutter"; "all that work went down the sewer";
       "pensions are in the toilet" [syn: gutter, sewer,
       toilet]

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "sewer":
   Singer, abri, antre, bog, bunker, burrow, cave, cavern, cesspool,
   cloaca, cloaca maxima, cove, drain, dugout, dump, foxhole,
   garbage dump, garmentmaker, grot, grotto, gutter, headchute, hole,
   kennel, lair, marsh, mire, needleman, needler, needlewoman,
   needleworker, piscina, quagmire, scupper, seamster, seamstress,
   sempster, septic tank, sewing machine, sink, sluice, sough,
   subterrane, subway, sump, swamp, tailor, tunnel, warren