If a noise is loud, the level of sound is very high and it can be easily heard. Someone or something that is loud produces a lot of noise.

If you describe something, especially a piece of clothing, as loud, you dislike it because it has very bright colours or very large, bold patterns which look unpleasant.

If you, for example, play music loud or speak loud, you do it so that the level of sound is very high and it can be easily heard.

If you say or read something out loud, you say it or read it so that it can be heard, rather than just thinking it.