1. In an imperceptible manner or to an imperceptible degree
   "the power of the Secretary of State in London increased gradually but imperceptibly"
   - unnoticeably

See also: imperceptible

Antonym: perceptibly

• airsick
• airsickness
• airside
• airspace
• airspeed
• airstream
• airstrip
• airt
• airtight
• airtime
• airwave
• airway
• airwoman
• airworthiness
• airworthy
• airy
• airy-fairy
• aisle
• ait
• aitch
• aitchbone
• Aix
• Aix galericulata
• Aix sponsa
• Aix-la-Chapelle