To go "out on a limb" means that you (1) put yourself at risk, (2) exert great effort, or (3) do something without support. Most of us have two legs ... imagine going out with only one leg - "out on *A* limb." You can definitely see that this person on only one leg lacks support, must make a great deal of effort, or is in a precarious/unstable/dangerous situation. Examples: (Meaning (1)): He hardly knew her, but he went out on a limb and asked for a date. (he put himself at risk of a rejection). (Meaning (2)): Did you know that he went out on a limb for you and covered your missed assignments? (he exerted a lot of effort to cover the assignments) (Meaning (3)): He went out on a limb and predicted who would win the race for mayor. (He had no support to make that prediction).

Out on a limb also means you are in a situation where you lack suppport.. He was pretty far out on a limb when he prediced who's going to win the match yesterday.. Anyways wait for natives to respond as well..

I don't mean to criticize, but I have never heard this expression used to mean "exert great effort" or "do something without support". "Out on a limb" means putting yourself at risk in some way. I do appreciate the example of going out with only one leg, but I am certain that the expression comes from climbing a tree, not having only one leg.

Out on a limb means to do something by your self, so if your going out somewhere ou dont know very much about, your going out on a limb.

Jianing... look at the comments in Brian's answer regarding "go".