Dictionary:

buckshee

  (bŭk'shē) Chiefly British.

1. Something extra or left over that is obtained free.
2. An extra ration.

1. Free of charge; gratis: “If they deposit these shares, too, in the scheme, they will get further buckshee shares on a one-for-one basis” (Economist).
2. Unsolicited; gratuitous: “The title was a bit of buckshee deceit, and had little to do with the plot” (Financial Times).

[Variant of BAKSHEESH.]

The adjective has one meaning:

Meaning #1: (British) free of charge