Source : Webster's Revised Unabridged Dictionary (1913)

Mustard \Mus"tard\, n. [OF. moustarde, F. moutarde, fr. L.
   mustum must, -- mustard was prepared for use by being mixed
   with must. See {Must}, n.]
   1. (Bot.) The name of several cruciferous plants of the genus
      {Brassica} (formerly {Sinapis}), as white mustard ({B.
      alba}), black mustard ({B. Nigra}), wild mustard or
      charlock ({B. Sinapistrum}).

   Note: There are also many herbs of the same family which are
         called mustard, and have more or less of the flavor of
         the true mustard; as, bowyer's mustard ({Lepidium
         ruderale}); hedge mustard ({Sisymbrium officinale});
         Mithridate mustard ({Thlaspi arvense}); tower mustard
         ({Arabis perfoliata}); treacle mustard ({Erysimum
         cheiranthoides}).

   2. A powder or a paste made from the seeds of black or white
      mustard, used as a condiment and a rubefacient. Taken
      internally it is stimulant and diuretic, and in large
      doses is emetic.

   {Mustard oil} (Chem.), a substance obtained from mustard, as
      a transparent, volatile and intensely pungent oil. The
      name is also extended to a number of analogous compounds
      produced either naturally or artificially.

Penny \Pen*ny\, n.; pl. {Pennies}or {Pence}. Pennies denotes the
   number of coins; pence the amount of pennies in value. [OE.
   peni, AS. penig, pening, pending; akin to D. penning, OHG.
   pfenning, pfenting, G. pfennig, Icel. penningr; of uncertain
   origin.]
   1. An English coin, formerly of copper, now of bronze, the
      twelfth part of an English shilling in account value, and
      equal to four farthings, or about two cents; -- usually
      indicated by the abbreviation d. (the initial of
      denarius).

   Note: ``The chief Anglo-Saxon coin, and for a long period the
         only one, corresponded to the denarius of the Continent
         . . . [and was] called penny, denarius, or denier.''
         --R. S. Poole. The ancient silver penny was worth about
         three pence sterling (see {Pennyweight}). The old
         Scotch penny was only one twelfth the value of the
         English coin. In the United States the word penny is
         popularly used for cent.

   2. Any small sum or coin; a groat; a stiver. --Shak.

   3. Money, in general; as, to turn an honest penny.

            What penny hath Rome borne, What men provided, what
            munition sent?                        --Shak.

   4. (Script.) See {Denarius}.

   {Penny cress} (Bot.), an annual herb of the Mustard family,
      having round, flat pods like silver pennies ({Thlaspi
      arvense}). --Dr. Prior.

   {Penny dog} (Zo["o]l.), a kind of shark found on the South
      coast of Britain: the tope.

   {Penny father}, a penurious person; a niggard. [Obs.]
      --Robinson (More's Utopia).

   {Penny grass} (Bot.), pennyroyal. [R.]

   {Penny post}, a post carrying a letter for a penny; also, a
      mail carrier.

   {Penny wise}, wise or prudent only in small matters; saving
      small sums while losing larger; -- used chiefly in the
      phrase, penny wise and pound foolish.

Source : WordNet®

Thlaspi arvense
     n : foetid Eurasian weed having round flat pods; naturalized
         throughout North America [syn: {field pennycress}, {French
         weed}, {fanweed}, {penny grass}, {stinkweed}, {mithridate
         mustard}]