leave without permission, unauthorized departure
Ronnie Biggs was doing time, until he done a bunk, now he says he's seen the light, and sold his soul for punk
by paul-e May 27, 2006
1 more definition
V. To escape or flee under incriminating circumstances.
"He has, to use the common phrase, done a bunk," replied Professor McGonagall, and a great cheer erupted from the Gryffindors, Hufflepuffs, and Ravenclaws." From Harry Potter and the Deathly Hallows
by JB 117 January 13, 2009