From BiblePortal Wikipedia

Morrish Bible Dictionary [1]

Besides the common use of this word in many connections, it is used in a special sense to carry the mind back into

a, eternity , when the Word was with God, and was God, by whom all things were made.  John 1:1-3;  Acts 15:18 (which should read 'from eternity'). Also to the eternity of Jehovah, 'the beginning and the end.'   Revelation 1:8;  Revelation 21:6;  Revelation 22:13 .

b, The creation, whether it was creating out of nothing or forming the heavens and the earth  Isaiah 64:4;  Hebrews 1:10 . Also the creation of man and woman.  Matthew 19:4,8;  Mark 10:6 .

c, The beginning of Christianity.   John 15:27;  John 16:4;  1 John 1:1;  1 John 3:11;  2 John 5,6 .

d, foundation or source , It is used also with a moral sense as a foundation or source, as in  Colossians 1:18;  Revelation 3:14 .

Webster's Dictionary [2]

(1): (p. pr. & vb. n.) of Begin

(2): (n.) That which is begun; a rudiment or element.

(3): (n.) The act of doing that which begins anything; commencement of an action, state, or space of time; entrance into being or upon a course; the first act, effort, or state of a succession of acts or states.

(4): (n.) That which begins or originates something; the first cause; origin; source.

(5): (n.) Enterprise.

King James Dictionary [3]

BEGIN'NING, ppr. First entering upon commencing giving rise or original taking rise or origin.

BEGIN'NING, n. The first cause origin.

I am the beginning and the ending.  Revelation 1

1. That which is first the first state commencement entrance into being.

In the beginning, God created the heaven and the earth.  Genesis 1

3. The rudiments, first ground or materials.

Mighty things from small beginnings grow

International Standard Bible Encyclopedia [4]

bē̇ - gin´ing ( ראשׁית , rē' - shı̄th  ; ἀρχή , archḗ ): The natural meaning of the word is with reference to time. The primitive Greek root means "to be long," "to draw out." Thus, it is used to refer to some point of time long drawn out, or long past ( Genesis 1:1 ). It is used also to express the inauguration of a particular event ( Exodus 12:2 ). The principal interest in the word centers in the use of it in  John 1:1 . It must be interpreted here by that which follows in the statement as to the relation of the Logos to the Eternal God and the use of the word "was." It is true that the word αρχε , archē cannot be separated from the idea of time, but when time began He already was, and therefore He was from eternity. See Time; Eternity .

Figurative: in a figurative sense it is used of that which is most excellent, the chief part (  Proverbs 1:7 ); of the most eminent person ( Colossians 1:18 ); the author ( Revelation 3:14 ).

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [5]

( בְּרֵאשַׁית , "in the beginning," liter. ally At the Head,  Genesis 1:1; Sept. and New Test. Ἐν Ἀρχῇ ), besides its ordinary import, was with the He. brews an idiomatic form of expression for eternity, q. d. Originally. In this sense it is employed alike by Moses and (in its Greek form) by the evangelist John ( John 1:1). (See Creation).

Our Lord is also emphatically styled the Beginning ( Ἀρχή ) both by Paul and John ( Colossians 1:18;  Revelation 1:8;  Revelation 3:14), and it is worthy of remark that the Greek philosophers expressed the First Cause of all things by the same word. (See Logos).