King James Dictionary 
OPINION, n. opin'yon. L. opinio, from opinor, to thing, Gr., L. suppono.
1. The judgment which the mind forms of any proposition, statement, theory or event, the truth or falsehood of which is supported by a degree of evidence that renders it probably, but does not produce absolute knowledge or certainty. It has been a received opinion that all matter is comprised in four elements. This opinion is proved by many discoveries to be false. From circumstances we form opinions respecting future events.
Opinion is when the assent of the understanding is so far gained by evidence of probability, that it rather inclines to one persuasion than to another, yet not without a mixture of uncertainty or doubting.
2. The judgment or sentiments which the mind forms of persons or their qualities. We speak of a good opinion, a favorable opinion, a bad opinion, a private opinion, and public or general opinion, &c.
Friendship gives a man a peculiar right and claim to the good opinion of his friend.
3. Settled judgment or persuasion as religious opinions political opinion. 4. Favorable judgment estimation.
In actions of arms, small matters are of great moment, especially when they serve to raise an opinion of commanders.
However, I have no opinion of these things -
Webster's Dictionary 
(1): ( n.) Obstinacy in holding to one's belief or impression; opiniativeness; conceitedness.
(2): ( n.) The formal decision, or expression of views, of a judge, an umpire, a counselor, or other party officially called upon to consider and decide upon a matter or point submitted.
(3): ( n.) The judgment or sentiment which the mind forms of persons or things; estimation.
(4): ( v. t.) To opine.
(5): ( n.) Favorable estimation; hence, consideration; reputation; fame; public sentiment or esteem.
(6): ( n.) That which is opined; a notion or conviction founded on probable evidence; belief stronger than impression, less strong than positive knowledge; settled judgment in regard to any point of knowledge or action.
Charles Buck Theological Dictionary 
Is that judgment which the mind forms of any proposition, for the truth or falsehood of which there is not sufficient evidence to produce absolute belief.
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
(from Latin opinor, to think) is a synonyme of belief, and measurably, too, of knowledge; but, while the last-named term can be applied to what is objectively and subjectively held as sufficient, and belief is applied to what is subjectively sufficient, opinion is properly applied only to a consciously insufficient judgment, or, as Sir Lewis has it: "The essential idea of opinion seems to be that it is a matter about which doubt can reasonably exist, as to which two persons can without absurdity think differently... Any proposition, the contrary of which can be maintained with probability, is matter of opinion" (Essay on Opinion). According to the last of these definitions, matter of opinion is opposed not to matter offact, but to matter of certainty. Thus the death of Charles I is fact — his authorship of Icon Basilike, an opinion. It is also used, however, to denote knowledge acquired by inference, as opposed to that acquired by perception. Thus that the moon gives light is matter of fact; that it is inhabited or uninhabited is matter of opinion. It has been proposed to discard from philosophical use these ambiguous expressions, and to divide knowledge, according to its sources, into matter of perception and matter of inference; and, as a cross division as to our conviction, into matter of certainty and matter of doubt. ‘ Subjective sufficiently is termed conviction (for myself); objective determination is termed certainty (for all). (See Knowledge).
International Standard Bible Encyclopedia 
ṓ - pin´yun ( דּע , dēa' , סעפּים , ṣe‛ippı̄m ): "Opinion" occurs only 5 times, thrice in Job ( Job 32:6 , Job 32:10 , Job 32:17 ) as the translation of dēa' , "knowledge," "opinion" (in the address of Elihu), and once of ṣe‛ippı̄m , from ṣā‛aph , "to divide or branch out," hence, division or party, unsettled opinion (in the memorable appeal of Elijah, "How long halt ye between two opinions?" 1 Kings 18:21 , the American Standard Revised Version "How long go ye limping between the two sides?"). In Ecclesiasticus 3:24, we have, "For many are deceived by their own vain opinion" ( hupolepsis , "a taking up," "a hasty judgment"), the Revised Version (British and American) The conceit of many hath led them astray.