Vine's Expository Dictionary of NT Words 
is one of two words translated "best" in the AV, but the only one so rendered in the RV. In Luke 15:22 "the best (robe)" is, lit., "the first (robe)," i.e., chief, principal, first in rank or quality. See Before , Beginning , Chief , First , Former.
"greater," is translated "best" in 1—Corinthians 12:31 , "the best gifts," greater, not in quality, but in importance and value. It is the comparative degree of megas, "great;" the superlative, megistos, is used only in 2—Peter 1:4 . See Elder , Greater and MORE.
King James Dictionary 
BEST, a. superlative. Eng.but Literally, most advanced, Hence,
1. Most good having good qualities in the highest degree applied indifferently to physical or moral subjects as, the best man the best road the best cloth the best abilities. This, like most, and other attributes, is often used without its noun, when the noun is obvious as, men are all sinners the best of them fail in the performance of duty. 2. Most advanced most accurate as the best scholar. 3. Most correct or complete as the best view of a landscape, or of a subject. 4. The best. This phrase is elliptical, and may be variously interpreted as, the utmost power the strongest endeavor the most, the highest perfection as, let a man do his best let him do a thing to the best of his power. 5. At best, in the best manner, in the utmost degree or extent, applicable to the case as, life is at best very short.
To make the best of, to carry to its greatest perfection to improve to the utmost as, to make the best of a sum of money, or a piece of land. Also, to permit the least possible inconvenience as, to make the best of fortune or a bad bargain.
The best of the way. We had made the best of our way to the city that is, the most, the greatest part of the distance. This is the primary sense of the word.
BEST, adv. In the highest degree beyond all other as, to love one best to like this best to please best.
1. To the advantage with the most ease as,"which instrument can you best use?" 2. With most profit or success as, money is best employed in manufactures this medicine will answer best in the present case. 3. Most intimately or particularly most correctly as, what is expedient is best known to himself.
Webster's Dictionary 
(1): (a.) Most; largest; as, the best part of a week.
(2): (a.) Having good qualities in the highest degree; most good, kind, desirable, suitable, etc.; most excellent; as, the best man; the best road; the best cloth; the best abilities.
(3): (a.) Most advanced; most correct or complete; as, the best scholar; the best view of a subject.
(4): (v. t.) To get the better of.
(5): (n.) Utmost; highest endeavor or state; most nearly perfect thing, or being, or action; as, to do one's best; to the best of our ability.
(6): (superl.) In the highest degree; beyond all others.
(7): (superl.) To the most advantage; with the most success, case, profit, benefit, or propriety.
(8): (superl.) Most intimately; most thoroughly or correctly; as, what is expedient is best known to himself.
International Standard Bible Encyclopedia 
Of five Hebrew originals the chief is טוב , ṭōbh , "good," expressing quality, character. Variously used of objects pleasing to the senses, feelings, mind, moral sense, e.g. "best of the land" ( Genesis 47:6 ); "of sheep" ( 1 Samuel 15:9 ); of persons "married to whom they think best" ( Numbers 36:6 ); of abode, "where it liketh (the Revised Version (British and American) "pleaseth") him best" ( Deuteronomy 23:16 ).
In Numbers 18:12 the revenues of the priests were to be "holy gifts," e.g. the "best of the oil," etc. ( חלב , ḥēlebh , "fat"); also Numbers 18:29 , Numbers 18:30 , Numbers 18:32 , the gifts of the heave-offering were to be "of all the best," indicating that the richest elements of life were to go into the support and service of the sanctuary. So "the choice (best) fruits" (זמרה , zı̄mrah , literally, "the song of the land"), a beautifully poetic expression for the most celebrated fruits ( Genesis 43:11 ); equally choice is פזז , pāzaz , "separate," "the finest (best) gold," hence "purified" ( 1 Kings 10:18 ).
Used but twice in the New Testament: (1) of spiritual gifts (κρεῖττον , kreı́tton , "better" the Revised Version (British and American) "greater"); 1 Corinthians 12:31 ); (2) of raiment (πρῶτος , prō̇tos , "first"), "best robe" ( Luke 15:22 ), of special significance as expressing the Father's lavish love for the repentant and returning sinner.