Arguably is the exact opposite of “something is sure and you shouldn’t even discuss it”.
It means, literally, capable of being argued; and if you look closely at your two definitions from dictionary.com you will see that they both support this meaning:
1.susceptible to debate, challenge, or doubt; questionable: Whether this is the best plan of action or not is arguable.
That is, arguments may be advanced on both sides of the question of whether this is the best plan of action.
2.susceptible to being supported by convincing or persuasive argument: Admirers agree that it is arguable he is the finest pianist of his generation.
That is, an argument may be advanced that he is the finest pianist of his generation.
The difference between the two lies in different meanings of the words argue/argument. An argument may represent either
- a) a single proposition or position and the reasons and evidence supporting it; this is the sense employed in definition 2.
- b) the competition between two opposed propositions, each with different reasons and evidence; this is the sense employed in definition 1.
But definition 2 does not support the sense that “something is sure and you shouldn’t even discuss it”. Even the pianist’s admirers do not advance the notion that his status is beyond argument; on the contrary, they say that a good case can be made for his being the finest of his generation.
I am at a loss to account for your dictionary’s offering that meaning. Are you sure it isn’t addressing inarguably or unarguably, which do in fact have that meaning? Neither is used to mean “incapable of being asserted”—an odd asymmetry, but that’s English for you.
Best Answer
Chance can have the implication of risk (of loss), but not always. On its face, the word chance simply means that a result could fail, not necessarily that there are negative consequences for failure. There often are negative consequences for failure, of course, but based on context and idiom the listener should be able to determine whether risk is involved.
Idiomatically, "take a chance" definitely has the implication that failure will have consequences. Idiomatically, "get a chance" does not have this implication, nor "grab/seize a chance". This may help you to remember: people typically want to "get" things. "Getting" things is nice! But you can "take" anything, including things you don't necessarily want. On the same note, while you can "take" anything, you typically won't "grab" or "seize" things you didn't intend to.
As a side note and background for how these idioms are used, a person will typically first hear "get a chance {to do something}" as a small child, where failure is definitely a possibility (because you are a small child without much skill) but consequences are minor (because you are a small child protected by adults). "Get a chance to kick the ball" for instance.
Regardless of why an idiom carries an implication-- without a negative consequence for failure, the word "chance" becomes very nearly synonymous with "opportunity". In fact, you can substitute "get an opportunity" for "get a chance" in nearly all instances of the phrase without changing the meaning. Likewise, "grab/seize an opportunity" for "grab/seize a chance".