PERIWIG is a 7 letter word that starts with P.

1. \Per"i*wig\, 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.
   
   

2. \Per"i*wig\, v. t. [imp. & p. p. {Perwigged}; p. pr. &
   vb. n. {Perwigging}.]
   To dress with a periwig, or with false hair. --Swift.