Unspeakable (adjective)

1. Too terrible or shocking to be described or mentioned.
2. Incapable of being expressed in words.
3. Too great or intense to be expressed or described adequately.

Origin:

Late 16th century; un- + speakable.

Examples:

1. The unspeakable horrors of the war.
2. The unspeakable pain was unbearable.
3. The unspeakable beauty of the sunset.
4. The unspeakable joy of being reunited with loved ones.
5. The unspeakable sadness of losing a loved one.