look up any word, like sex:
In Devon (West of England), an idle, slow and incompetent person who is no use to man nor beast. Just like a slack fanny (whether British or American), someone who does a poor job of whatever they are meant to be doing.
'That Pete's such a slack fanny. Three bloody years I've been waiting for him to look at my roof.'
by mockschmock December 07, 2006