Under its original spelling Philistine
, it's defined as those who are smug, ignorant and indifferent to intellectual pursuits.
"Phyllis-teen" (often shortened to PT) expounds upon the original definition and refers to women of little, intrinsic value - often named Phyllis, Lisa or Courtney. A woman whose narrow view on life often includes a disdain of all cultures (except her own), pure hatred for children and a life focused on having her partner pay for all her shit because she's a spoiled beeyotch and he's a fucktard
Essentially, phyllis-teens are spoiled skanks and racist baby-haters. A phyllis-teen would eat a child's innards and turn its skin into a Gucci belt if given the chance.