Examples might look like this:
flat out like a lizard drinking
Extremely busy, at top speed. This is word play on two different meanings of the standard English ‘flat out’. The literal sense is to lie fully stretched out (like a lizard), and the figurative sense means as fast as possible. The phrase also alludes to the rapid tongue-movement of a drinking lizard. It is sometimes shortened, as in ‘we’re flat out like a lizard trying to meet the deadline’.
(Australian National Dictionary Centre Research School of Humanities) http://www.anu.edu.au/andc/res/aus_words/aewo...
(Same link as you put in, simone, but the Leo team doesn't have to search for the phrase, and this way it doesn't look like it might just be a joker posting nonsense.)
"The Australian expressions - flat out, like a lizard drinking and flat out, like a lizard on a log, are a little easier to interpret. They clearly allude to lying flat on one's face. These are known from around the time of WWII and are recorded in Sidney John Baker's, The drum: Australian character and slang, 1959:
"Ideas of lying flatly (on one's face, not one's back) and of travelling or working at great speed are recorded in the phrases 'flat out like a lizard drinking' and 'flat out like a lizard on a log'."
They are rarely used literally though, i.e. to mean lying flat out, but are just an emphatic form of the usual meaning of 'flat out'. " http://www.phrases.org.uk/meanings/flat-out.html
"LAWS: OK, I appreciate your time very much Kevin because I know you are in for a busy few weeks, I suppose I am too.
RUDD: Well, flat out like lizards drinking.
LAWS: Yeah, isn’t that a good old Aussie expression.
RUDD: It is, I love it.
LAWS: Yes, flat out like a lizard drinking.
RUDD: I’m in battle and I’m flat out like a lizard drinking.
LAWS: Good to talk to you Kevin and thanks for your time. " http://www.alp.org.au/media/1007/riloo152.php
(website of Australian Labour Party)