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

See also: unexpected

• average out
• averagely
• averageness
• Averell Harriman
• averment
• Averrhoa
• binoculars
• binomial
• binomial distribution
• binomial theorem
• binominal
• bint
• binturong
• binuclear
• binucleate
• binucleated
• bio
• bio lab
• bioaccumulate
• bioarm
• bioassay
• bioattack
• bioavailability
• biocatalyst
• biocatalytic