imperceptibly

Meanings

1. 1
   adv

   in an imperceptible manner or to an imperceptible degree

   the power of the Secretary of State in London increased gradually but imperceptibly

2. 2
   adv

   Not noticeably; such that it cannot be detected, through being too small or too fast, etc.

   No one noticed that he had moved imperceptibly backwards.

Etymology

From imperceptible + -ly.