The Collaborative International Dictionary of English v.0.48:

Frock \Frock\ (fr[o^]k), n. [F. froc a monk's cowl, coat,
   garment, LL. frocus, froccus, flocus, floccus, fr. L. floccus
   a flock of wool; hence orig., a flocky cloth or garment; cf.
   L. flaccus flabby, E. flaccid.]
   1. A loose outer garment; especially, a gown forming a part
      of European modern costume for women and children; also, a
      coarse shirtlike garment worn by some workmen over their
      other clothes; a smock frock; as, a marketman's frock.
      [1913 Webster]

   2. A coarse gown worn by monks or friars, and supposed to
      take the place of all, or nearly all, other garments. It
      has a hood which can be drawn over the head at pleasure,
      and is girded by a cord.
      [1913 Webster]

   Frock coat, a body coat for men, usually double-breasted,
      the skirts not being in one piece with the body, but sewed
      on so as to be somewhat full.

   Smock frock. See in the Vocabulary.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Frock \Frock\, v. t.
   1. To clothe in a frock.
      [1913 Webster]

   2. To make a monk of. Cf. Unfrock.
      [1913 Webster]

WordNet (r) 3.0 (2006):

frock
    n 1: a habit worn by clerics
    2: a one-piece garment for a woman; has skirt and bodice [syn:
       dress, frock]
    v 1: put a frock on

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "frock":
   bib and tucker, cloak, costume, dress, duds, garment, gown, habit,
   jupe, mantle, rag, raiment, rig, robe, skirt, suit, togs, vestment,
   vesture