1. In a way that was not expected
   - out of the blue 
2. Without advance planning
   - by chance, accidentally, circumstantially

See also: unexpected

• ryegrass
• Rynchopidae
• Rynchops
• ryot
• Rypticus
• Ryukyu Islands
• Ryukyuan
• Réaumur
• réchauffé
• rémoulade
• röntgen
• s
• S wrench
• S-shape
• s-shaped
• S. S. Van Dine
• S. Smith Stevens
• SA
• SA node
• Saale
• Saale glaciation
• Saale River
• Saame
• Saami
• SAARC