D defs.my
Entry 1 sense Webster, 1913

billfold

/(bĭl" fōld`)/ · bill·fold · IPA /ˈbɪlˌfoʊld/
01 A small, thin, flat container, usually made of leather or imitation leather, having a pocket of a size just large enough to hold paper curr…
  1. 1.
    A small, thin, flat container, usually made of leather or imitation leather, having a pocket of a size just large enough to hold paper currency and folded over once to fit in the pocket of one's clothing; it is a type of wallet, but having fewer compartments than the typical wallet.