From BiblePortal Wikipedia

Webster's Dictionary [1]

(1): ( n.) One who employs another to act for him, - as distinguished from an agent.

(2): ( a.) Highest in rank, authority, character, importance, or degree; most considerable or important; chief; main; as, the principal officers of a Government; the principal men of a state; the principal productions of a country; the principal arguments in a case.

(3): ( a.) Of or pertaining to a prince; princely.

(4): ( n.) A leader, chief, or head; one who takes the lead; one who acts independently, or who has controlling authority or influence; as, the principal of a faction, a school, a firm, etc.; - distinguished from a subordinate, abettor, auxiliary, or assistant.

(5): ( n.) The chief actor in a crime, or an abettor who is present at it, - as distinguished from an accessory.

(6): ( n.) A chief obligor, promisor, or debtor, - as distinguished from a surety.

(7): ( n.) One of turrets or pinnacles of waxwork and tapers with which the posts and center of a funeral hearse were formerly crowned.

(8): ( n.) A thing of chief or prime importance; something fundamental or especially conspicuous.

(9): ( n.) A capital sum of money, placed out at interest, due as a debt or used as a fund; - so called in distinction from interest or profit.

(10): ( n.) The construction which gives shape and strength to a roof, - generally a truss of timber or iron, but there are roofs with stone principals. Also, loosely, the most important member of a piece of framing.

(11): ( n.) In English organs the chief open metallic stop, an octave above the open diapason. On the manual it is four feet long, on the pedal eight feet. In Germany this term corresponds to the English open diapason.

(12): ( n.) A heirloom; a mortuary.

(13): ( n.) The first two long feathers of a hawk's wing.

(14): ( n.) A principal or essential point or rule; a principle.

King James Dictionary [2]

PRIN'CIPAL, a. L. principalis, from princeps.

1. Chief highest in rank, character or respectability as the principal officers of a government the principal men of a city, town, or state.  Acts 25 .  1 Chronicles 24 2. Chief most important or considerable as the principal topics of debate the principal arguments in a case the principal points of law the principal beams of a building the principal productions of a country.

Wisdom is the principal thing.  Proverbs 4

3. In law, a principal challenge, is where the cause assigned carries with it prima facie evidence of partiality, favor or malice. 4. In music, fundamental.

PRIN'CIPAL, n. A chief or head one who takes the lead as the principal of a faction, an insurrection or mutiny.

1. The president, governor, or chief in authority. We apply the word to the chief instructor of an academy or seminary of learning. 2. In law, the actor or absolute perpetrator of a crime, or an abettor. A principal in the first degree, is the absolute perpetrator of the crime a principal in the second degree, is one who is present, aiding and abetting the fact to be done distinguished from an accessory. In treason, all persons concerned are principals. 3. In commerce, a capital sum lent on interest, due as a debt or used as a fund so called in distinction from interest or profits.

Taxes must be continued, because we have no other means for paying off the principal.

4. One primarily engaged a chief party in distinction from an auxiliary.

We were not principals, but auxiliaries in the war.

Vine's Expository Dictionary of NT Words [3]

1: Πρῶτος (Strong'S #4413 — Adjective — protos — pro'-tos )

"first," is translated "principal men" in the RV of  Luke 19:47;  Acts 25:2 . See Chief , A.

 Acts 25:23  Job 39:28

International Standard Bible Encyclopedia [4]

prin´si - pal  : Appears in the King James Version as a translation of nine Hebrew words (fewer in the Revised Version (British and American)), in one case (  Isaiah 28:25 ) being used quite wrongly and in  2 Kings 25:19 (  Jeremiah 52:25 );  1 Chronicles 24:31 gives a wrong sense (all corrected in the Revised Version (British and American)). In   1 Kings 4:5 , "principal officer" (the American Standard Revised Version "chief minister") is an arbitrary translation of kōhēn to avoid "priest" (so the English Revised Version; compare  2 Samuel 8:18 ).