1. Not observed
   - unseen 
2. Not observed
   "managed to slip away unobserved"

See also: undetected, unnoticed

• circuitously
• circuitry
• circuity
• circular
• circular file
• circular function
• circular measure
• circular plane
• circular saw
• circular-knit
• circularisation
• circularise
• circularity
• circularization
• circularize
• circularly
• circulate
• circulating
• circulating decimal
• circulating library
• circulation
• circulative
• circulator
• circulatory
• circulatory failure