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

See also: unexpected

• Trachinotus carolinus
• Trachinotus falcatus
• Trachipteridae
• Trachipterus
• Trachipterus arcticus
• trachodon
• trachodont
• trachoma
• Trachurus
• Trachurus symmetricus
• Trachurus trachurus
• trachyte
• tracing
• tracing paper
• tracing routine
• track
• track and field
• track down
• track event
• track meet
• track record
• track star
• track-to-track seek time
• trackable
• trackage