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

• fluorescence microscopy
• fluorescent
• fluorescent dye
• fluorescent fixture
• fluorescent lamp
• fluoridate
• fluoridation
• fluoride
• fluoridisation
• fluoridise
• fluoridization
• fluoridize
• fluorine
• fluorite
• fluoro-
• fluoroboric acid
• fluoroboride
• fluorocarbon
• fluorocarbon plastic
• fluorochrome
• fluoroform
• fluoroscope
• fluoroscopy
• fluorosis
• fluorouracil