speculate

American Heritage® Dictionary of the English Language, Fourth Edition

1. v. To meditate on a subject; reflect.
2. v. To engage in a course of reasoning often based on inconclusive evidence. See Synonyms at think.
3. v. To engage in the buying or selling of a commodity with an element of risk on the chance of profit.
4. v. To assume to be true without conclusive evidence: speculated that high cholesterol was a contributing factor to the patient's health problems.

Century Dictionary and Cyclopedia

1. To view as from a watch-tower or observatory; observe.
2. To take a discriminating view of; consider attentively; speculate upon; examine; inspect: as, to speculate the nature of a thing.
3. To pursue truth by thinking, as by mathematical reasoning, by logical analysis, or by the review of data already collected.
4. To take a discursive view of a subject or subjects; note diverse aspects, relations, or probabilities; meditate; conjecture: often implying absence of definite method or result.
5. To invest money for profit upon an uncertainty; take the risk of loss in view of possible gain; make a purchase or purchases, as of something liable to sudden fluctuations in price or to rapid deterioration, on the chance of selling at a large advance: as, to speculate in stocks.

Wiktionary

1. v. intransitive to think, meditate or reflect on a subject; to deliberate or cogitate
2. v. intransitive to make an inference based on inconclusive evidence; to surmise or conjecture
3. v. intransitive, business, finance to make a risky trade in the hope of making a profit; to venture or gamble

GNU Webster's 1913

1. v. To consider by turning a subject in the mind, and viewing it in its different aspects and relations; to meditate; to contemplate; to theorize
2. v. (Philos.) To view subjects from certain premises given or assumed, and infer conclusions respecting them a priori.
3. v. (Com.) To purchase with the expectation of a contingent advance in value, and a consequent sale at a profit; -- often, in a somewhat depreciative sense, of unsound or hazardous transactions.
4. v. rare To consider attentively.

WordNet 3.0

1. v. talk over conjecturally, or review in an idle or casual way and with an element of doubt or without sufficient reason to reach a conclusion
2. v. to believe especially on uncertain or tentative grounds
3. v. invest at a risk
4. v. reflect deeply on a subject