The Collaborative International Dictionary of English v.0.48:

Periwig \Per"i*wig\ (p[e^]r"[i^]*w[i^]g), n. [OE. perrwige,
   perwicke, corrupt. fr. F. perruque; cf. OD. peruyk, from
   French. See Peruke, and cf. Wig.]
   A headdress of false hair, usually covering the whole head,
   and representing the natural hair; a wig. --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Periwig \Per"i*wig\, v. t. [imp. & p. p. Perwigged
   (p[e^]r"[i^]*w[i^]gd); p. pr. & vb. n. Perwigging
   (p[e^]r"[i^]*w[i^]g*g[i^]ng).]
   To dress with a periwig, or with false hair. --Swift.
   [1913 Webster]

WordNet (r) 3.0 (2006):

periwig
    n 1: a wig for men that was fashionable in the 17th and 18th
         centuries [syn: periwig, peruke]