1. in a way that cannot be explained or understood

Examples

• She felt unaccountably sad after hearing the good news.
• The machine stopped working unaccountably in the middle of the presentation.
• He was unaccountably nervous before the simple interview.
• The temperature dropped unaccountably during the summer afternoon.
• The dog became unaccountably aggressive toward strangers.
• Her mood changed unaccountably from cheerful to melancholy.