1. to an extreme degree that cannot be adequately expressed in words
2. in a way that is too shocking, horrible, or offensive to be described

Examples

• The view from the mountaintop was unspeakably beautiful.
• She was unspeakably grateful for their help during the crisis.
• The conditions in the prison were unspeakably cruel.
• He felt unspeakably sad after hearing the news.
• The tragedy was unspeakably horrible.
• The dessert was unspeakably delicious.
• The betrayal left her unspeakably hurt.