1. [syn: imperceptibly, unnoticeably]
The Collaborative International Dictionary of English v.0.48:
Imperceptible \Im`per*cep"ti*ble\, a. [Pref. im- not +
perceptible: cf. F. imperceptible.]
Not perceptible; not to be apprehended or cognized by the
senses; not discernible by the mind; not easily apprehended.
Almost imperceptible to the touch. --Dryden.
Its operation is slow, and in some cases almost
-- Im`per*cep"ti*ble*ness, n. -- Im`per*cep"ti*bly, adv.
Their . . . subtilty and imperceptibleness. --Sir M.
WordNet (r) 3.0 (2006):
adv 1: in an imperceptible manner or to an imperceptible degree;
"the power of the Secretary of State in London increased
gradually but imperceptibly" [syn: imperceptibly,
unnoticeably] [ant: noticeably, observably,