Green’s Dictionary of Slang

(Aus.) a useless, foolish, depressing person.

1949		R. Park Poor Man’s Orange 181: Of all the nice boys going to Luna Park [,...] she had to draw this droob.
1959		Baker Drum viii. 61: ‘Nong’ (or the duplicated form ‘nong-nong’) was equivalent not only to dill, but also to drube, dope, and drongo.
1985		B. Humphries Traveller’s Tool 98: ‘You’d have to be a bit of a droob, wouldn’t you?’ said Jacqui.