1. In an imperceptible manner or to an imperceptible degree
   - imperceptibly

See also: unnoticeable

• opposite word
• oppositely
• oppositeness
• opposition
• oppositionist
• oppositive
• oppress
• oppressed
• oppression
• oppressive
• oppressively
• oppressiveness
• oppressor
• opprobrious
• opprobriously
• opprobrium
• oppugn
• oppugnant
• Ops
• Opsanus tau
• opsin
• opsonin
• opsonisation
• opsonise
• opsonization