speculation

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Reasoning based on inconclusive evidence; conjecture or supposition.
• noun A conclusion, opinion, or theory reached by conjecture.
• noun Archaic Contemplation or consideration of a subject; meditation.
• noun Engagement in risky business transactions on the chance of quick or considerable profit.
• noun A commercial or financial transaction involving speculation.

from The Century Dictionary.

• noun The act or state of speculating, or of seeing or looking; intelligent contemplation or observation; a viewing; inspection.
• noun The pursuit of truth by means of thinking, especially mathematical reasoning and logical analysis; meditation; deep and thorough consideration of a theoretical question.
• noun In philosophy, sometimes, a purely a priori method of philosophizing: but commonly in philosophy the word has the meaning 2, above.
• noun The investing of money at a risk of loss on the chance of unusual gain; specifically, buying and selling, not in the ordinary course of commerce for the continuous marketing of commodities, but to hold in the expectation of selling at a profit upon a change in values or market rates.
• noun A game at cards, the leading principle of which is the purchase of an unknown card on the calculation of its probable value, or of a known card on the chance of no better appearing during the game, a part of the pack not being dealt.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of speculating.
• noun obsolete Examination by the eye; view.
• noun Mental view of anything in its various aspects and relations; contemplation; intellectual examination.
• noun (Philos.) The act or process of reasoning a priori from premises given or assumed.
• noun (Com.) The act or practice of buying land, goods, shares, etc., in expectation of selling at a higher price, or of selling with the expectation of repurchasing at a lower price; a trading on anticipated fluctuations in price, as distinguished from trading in which the profit expected is the difference between the retail and wholesale prices, or the difference of price in different markets.
• noun Any business venture in involving unusual risks, with a chance for large profits.
• noun A conclusion to which the mind comes by speculating; mere theory; view; notion; conjecture.
• noun obsolete Power of sight.
• noun A game at cards in which the players buy from one another trumps or whole hands, upon a chance of getting the highest trump dealt, which entitles the holder to the pool of stakes.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The process of thinking or meditating on a subject
• noun A judgement or conclusion reached by speculating
• noun business, finance An investment involving higher than normal risk in order to obtain a higher than normal return

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an investment that is very risky but could yield great profits
• noun a message expressing an opinion based on incomplete evidence
• noun continuous and profound contemplation or musing on a subject or series of subjects of a deep or abstruse nature
• noun a hypothesis that has been formed by speculating or conjecturing (usually with little hard evidence)