Difference between Mull Over and Speculate

MULL OVER vs SPECULATE: VERB

To think, meditate or reflect on a subject; to deliberate or cogitate
To make an inference based on inconclusive evidence; to surmise or conjecture
To make a risky trade in the hope of making a profit; to venture or gamble
Reflect deeply on a subject
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
To believe especially on uncertain or tentative grounds
Invest at a risk

To engage in a course of reasoning often based on inconclusive evidence; conjecture or theorize.
To engage in the buying or selling of a commodity with an element of risk on the chance of profit.
To assume to be true without conclusive evidence.
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.
To view subjects from certain premises given or assumed, and infer conclusions respecting them a priori.
To consider by turning a subject in the mind, and viewing it in its different aspects and relations; to meditate; to contemplate; to theorize

To view as from a watch-tower or observatory; observe.
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.
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.
To pursue truth by thinking, as by mathematical reasoning, by logical analysis, or by the review of data already collected.
To take a discriminating view of; consider attentively; speculate upon; examine; inspect: as, to speculate the nature of a thing.

Turn to, Take to, Get into, Deal with, Look forward to, Think over, Chew over, Muse, Meditate, Reflect, Speculate, Ruminate, Contemplate, Ponder, Mull

Mull over, Hypothecate, Job, Meditate, Muse, Reflect, Suppose, Ruminate, Mull, Contemplate, Ponder, Theorise, Conjecture, Hypothesize, Theorize

Turn to, Take to, Get into, Deal with, Look forward to, Think over, Chew over, Muse, Meditate, Reflect, Speculate, Ruminate, Contemplate, Ponder, Mull

Guess, Believe, Think over, Chew over, Job, Meditate, Muse, Reflect, Suppose, Ruminate, Mull, Contemplate, Ponder, Theorise, Conjecture