1. not planned or intended in advance; happening without preparation

Examples

• The meeting was completely unplanned and happened by chance.
• We took an unplanned detour through the mountains.
• Her pregnancy was unplanned but welcomed.
• The power outage caused an unplanned delay in the presentation.
• They made an unplanned stop at the roadside diner.
• The unplanned expenses put a strain on their budget.