Posted by Jon gives the etymology here.
In summary, it means that the Fed is very close to acting.
When used at the Dec 2000 meeting, it presaged an inter-meeting move for example – but it has not done so every time.
I wonder why Jon posted this today?
This plus his earlier article on how central banks are “Holding Fire—for Now—but Laying Plans” suggests to me that the Fed is alarmed at the ECB’s fail last night, and willing to step in to support markets if confidence totally collapses and equities start tanking.
ricardian ambivalence 
Well, Hilsenrath notes that Bernanke used the expression immediately post-Lehman and that didn’t stop the crash! They better get their skates on because they are running out of time.
It means you do not have any guts
Agreed – they needed more courage last meeting.
Sent from my iPad
The problem is in Europe. They can’t do anything about that. Actually they can’t even depreciate the US$ this time vs the EURO, can they?
Sure there is a limit to what they might achieve – but it would help a bit … That is why they needed courage – to take the probable near term gain despite the low probability of more medium term trouble when they exit.
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But it looks like just the talking of possible further easing is doing the job all right!
i have heard it said that the Fed knows its optimal strategy is to keep it on the table and not do anything … i am not so sure — as i do think that there is a useful change in expectations and hence asset allocation when they announce these policies — but it’s a plausible story as balance sheet expansion does seem to make yields rise in the short term.