The Collaborative International Dictionary of English v.0.48:

Genus \Ge"nus\ (j[=e]"n[u^]s), n.; pl. Genera. [L., birth,
   race, kind, sort; akin to Gr. ?. See Gender, and cf.
   Benign.]
   [1913 Webster]
   1. (Logic) A class of objects divided into several
      subordinate species; a class more extensive than a
      species; a precisely defined and exactly divided class;
      one of the five predicable conceptions, or sorts of terms.
      [1913 Webster]

   2. (Biol.) An assemblage of species, having so many
      fundamental points of structure in common, that in the
      judgment of competent scientists, they may receive a
      common substantive name. A genus is not necessarily the
      lowest definable group of species, for it may often be
      divided into several subgenera. In proportion as its
      definition is exact, it is natural genus; if its
      definition can not be made clear, it is more or less an
      artificial genus.
      [1913 Webster]

   Note: Thus in the animal kingdom the lion, leopard, tiger,
         cat, and panther are species of the Cat kind or genus,
         while in the vegetable kingdom all the species of oak
         form a single genus. Some genera are represented by a
         multitude of species, as Solanum (Nightshade) and Carex
         (Sedge), others by few, and some by only one known
         species.
         [1913 Webster]

   Subaltern genus (Logic), a genus which may be a species of
      a higher genus, as the genus denoted by quadruped, which
      is also a species of mammal.

   Summum genus [L.] (Logic), the highest genus; a genus which
      can not be classed as a species, as being.
      [1913 Webster]

WordNet (r) 3.0 (2006):

genus
    n 1: a general kind of something; "ignore the genus communism"
    2: (biology) taxonomic group containing one or more species

Moby Thesaurus II by Grady Ward, 1.0:

80 Moby Thesaurus words for "genus":
   antonomasia, binomial nomenclature, biosystematics, biosystematy,
   biotype, blood, branch, brand, breed, cast, character, clan, class,
   classification, color, denomination, description, designation,
   family, feather, form, genotype, genre, glossology, grain, ilk,
   kidney, kin, kind, kingdom, label, line, lot, make, manner, mark,
   mold, nature, nomenclature, number, onomastics, onomatology, order,
   orismology, persuasion, phylum, place-names, place-naming,
   polyonymy, race, section, series, shape, sort, species, stamp,
   strain, stripe, style, subclass, subfamily, subgenus, subkingdom,
   suborder, subspecies, subtribe, superclass, superfamily,
   superorder, superspecies, systematics, taxonomy, terminology,
   the like of, the likes of, toponymy, tribe, trinomialism, type,
   variety



Bouvier's Law Dictionary, Revised 6th Ed (1856):

GENUS. It denotes the number of beings, or objects, which agree in certain
general properties, common to them all, so that genus is, in fact, only an
abstract idea, expressed by some general name or term; or rather a name or
term, to signify what is called au abstract idea. Thus, goods is the generic
name, and includes, generally, all personal property; but this word may be
restrained, particularly in bequests to such goods as are of the same kind
as those previously enumerated. Vide 3 Ves. 311 11 Ves. 657; 1 Eq. Cas. Ab.
201, pl. 14; 2 Ves. sen. 278, 280; Dig. 50, 17, 80; Id. 12, 1, 2, 3.