The Collaborative International Dictionary of English v.0.48:
Dak \Dak\ (d[add]k or d[aum]k), n. [Hind. [dsdot][=a]k.] Post; mail; also, the mail or postal arrangements; -- spelt also dawk, and dauk. [India] [1913 Webster] Dak boat, a mail boat. --Percy Smith. Dak bungalow, a traveler's rest-house at the end of a dak stage. To travel by dak, to travel by relays of palanquins or other carriage, as fast as the post along a road.