The Collaborative International Dictionary of English v.0.48:

Lather \Lath"er\ (l[a^][th]"[~e]r), n. [AS. le['a][eth]or niter,
   in le['a][eth]orwyrt soapwort; cf. Icel. lau[eth]r; perh.
   akin to E. lye.]
   1. Foam or froth made by soap moistened with water.
      [1913 Webster]

   2. Foam from profuse sweating, as of a horse.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lather \Lath"er\, v. t. [imp. & p. p. Lathered
   (l[a^][th]"[~e]rd); p. pr. & vb. n. Lathering.] [AS.
   l[=e][eth]rian to lather, anoint. See Lather, n. ]
   To spread over with lather; as, to lather the face.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lather \Lath"er\, v. i.
   To form lather, or a froth like lather; to accumulate foam
   from profuse sweating, as a horse.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lather \Lath"er\, v. t. [Cf. Leather.]
   To beat severely with a thong, strap, or the like; to flog.
   [Low]
   [1913 Webster] Lathereeve

WordNet (r) 3.0 (2006):

lather
    n 1: the froth produced by soaps or detergents [syn: soapsuds,
         suds, lather]
    2: agitation resulting from active worry; "don't get in a stew";
       "he's in a sweat about exams" [syn: fret, stew, sweat,
       lather, swither]
    3: a workman who puts up laths
    4: the foam resulting from excessive sweating (as on a horse)
    v 1: beat severely with a whip or rod; "The teacher often
         flogged the students"; "The children were severely
         trounced" [syn: flog, welt, whip, lather, lash,
         slash, strap, trounce]
    2: form a lather; "The shaving cream lathered"
    3: exude sweat or lather; "this unfit horse lathers easily"
    4: rub soap all over, usually with the purpose of cleaning [syn:
       soap, lather]