From BiblePortal Wikipedia

King James Dictionary [1]

TER'RIBLE, a. L. terribilis, from terreo, to frighten.

1. Frightful adapted to excite terror dreadful formidable.

Prudent in peace, and terrible in war.

The form of the image was terrible.  Daniel 2

2. Adapted to impress dread, terror or solemn awe and reverence.

The Lord thy God is among you, a mighty God and terrible.  Deuteronomy 7

Let them praise thy great and terrible name, for it is holy.  Psalms 99

He hath done for thee these great and terrible things, which thine eyes have seen.  Deuteronomy 10

3. adv. Severely very so as to give pain as terrible cold a colloquial phrase.

Webster's Dictionary [2]

(1): ( a.) Adapted or likely to excite terror, awe, or dread; dreadful; formidable.

(2): ( a.) Excessive; extreme; severe.

Vine's Expository Dictionary of NT Words [3]

 Hebrews 12:21Fearful