From BiblePortal Wikipedia

Vine's Expository Dictionary of NT Words [1]

1: Μέγας (Strong'S #3173 — Adjective — megas — meg'-as )

"great," is used, besides other meanings, of intensity, as, e.g., of the force of a voice, e.g.,  Matthew 27:46,50; in the following the RV has "great" for the AV, "loud,"  Revelation 5:2,12;  6:10;  7:2,10;  8:13;  10:3;  12:10;  14:7,9,15,18 . See Great.

Webster's Dictionary [2]

(1): ( superl.) Having, making, or being a strong or great sound; noisy; striking the ear with great force; as, a loud cry; loud thunder.

(2): ( superl.) Ostentatious; likely to attract attention; gaudy; as, a loud style of dress; loud colors.

(3): ( adv.) With loudness; loudly.

(4): ( superl.) Emphatic; impressive; urgent; as, a loud call for united effort.

(5): ( superl.) Clamorous; boisterous.

King James Dictionary [3]

LOUD, a. L. laudo, to praise, and with a prefix, plaudo. Heb.

1. Having a great sound high sounding noisy striking the ear with great force as a loud voice a loud cry loud thunder. 2. Uttering or making a great noise as loud instruments.  2 Chronicles 30 . 3. Clamorous noisy.

She is loud and stubborn.  Proverbs 7 .

4. Emphatical impressive as a loud call to avoid danger.