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

• objurgate
• objurgation
• objurgatory
• oblanceolate
• oblanceolate leaf
• oblast
• oblate
• oblateness
• oblation
• obligate
• obligate anaerobe
• obligated
• obligation
• obligational
• obligato
• obligatorily
• obligatory
• oblige
• obliged
• obligee
• obliger
• obliging
• police constable
• police court
• police cruiser