Definitions
from The American Heritage® Dictionary of the English Language, 4th Edition
 n. The quality or condition of being probable; likelihood.
 n. A probable situation, condition, or event: Her election is a clear probability.
 n. The likelihood that a given event will occur: little probability of rain tonight.
 n. Statistics A number expressing the likelihood that a specific event will occur, expressed as the ratio of the number of actual occurrences to the number of possible occurrences.
 idiom in all probability Most probably; very likely.
from Wiktionary, Creative Commons Attribution/ShareAlike License
 n. the state of being probable; likelihood
 n. an event that is likely to occur
 n. the relative likelihood of an event happening
 n. a number, between 0 and 1, expressing the precise likelihood of an event happening
from the GNU version of the Collaborative International Dictionary of English
 n. The quality or state of being probable; appearance of reality or truth; reasonable ground of presumption; likelihood.
 n. That which is or appears probable; anything that has the appearance of reality or truth.
 n. Likelihood of the occurrence of any event in the doctrine of chances, or the ratio of the number of favorable chances to the whole number of chances, favorable and unfavorable. See 1st Chance, n., 5.
from The Century Dictionary and Cyclopedia
 n. The state or character of being probable; likelihood; appearance of truth; that state of a case or question of fact which results from superior evidence or preponderation of argument on one side, inclining the mind to receive that as the truth, but leaving some room for doubt.
 n. Quantitatively, that character of an argument or proposition of doubtful truth which consists in the frequency with which like propositions or arguments are found true in the course of experience.
 n. Anything that has the appearance of reality or truth.
 n. A statement of what is likely to happen; a forecast: applied in the plural by Cleveland Abbe to his daily weatherpredictions in Cincinnati in 1869, and subsequently adopted by General Myer to designate the official weatherforecasts of the United States Signal Service. The same term had been similarly used by Leverrier in Paris since 1859.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
 n. a measure of how likely it is that some event will occur; a number expressing the ratio of favorable cases to the whole number of cases possible
 n. the quality of being probable; a probable event or the most probable event
Etymologies
Examples

It is a doubt founded on a _positive_ opinion against the existence of the law, or its applicability to the case in point, an opinion fraught with probability, _solid, comparative, practical probability_.

Note that it does not mean it will happen, just that the probability is approaching 1 or unity.

Embracing Some Risk Two certified financial planners and a finance professor have come up with a system that manages what they call the "probability of failure."

Whether both mutations happen in one individual, or one in a parent and the next in that individual's offspring, without the benefit of selection to expand the first mutation within the population, the probability is the same.

So, the probability is my child will opt for the Jesus movement.

Two certified financial planners and a finance professor have come up with a system that manages what they call the "probability of failure."

So, Hacking argues, what we call probability was not an object of thought that existed in embryo to become fully developed when some social need or technological opportunity encouraged mathematicians to study it more carefully.

As long as the probability is not zero, then if the universe is spatially infinite we should expect life to arise somewhere in the infinite universe ….

The world has not shown me that understanding of elementary probability is widespread, so I worry that these kind of tools will be misused/misunderstood.

In Uttar Pradesh, a woman has one in 42 lifetime risks of maternal death, the probability is just one in 500 in Kerala, the report says, according to PTI reports.
oroboros commented on the word probability
"It may be that the race is not always to the swift, nor the battle to the strong  but that is the way to bet."
Damon Runyon
September 27, 2007