7 дней назад · unable to be noticed or felt because of being very slight: She heard a faint, almost imperceptible cry.

The meaning of IMPERCEPTIBILITY is the quality or state of being imperceptible.

7 дней назад · in a very slight way that a person is unable to notice or feel: Gradually, almost imperceptibly, her condition had worsened.

the property of being imperceptible by the mind or the senses.

adjective. very slight, gradual, or subtle: the imperceptible slope of the road. not perceptible; not perceived by or affecting the senses.

not plain or distinct to the senses or the mind; esp., so slight, gradual, subtle, etc. as not to be easily perceived.

There are two meanings listed in OED's entry for the noun imperceptibility. See 'Meaning & use' for definitions, usage, and quotation evidence.

​very small and therefore unable to be seen or felt. imperceptible changes in temperature; There was an almost imperceptible pause as she gathered her ...

the quality or condition of being too slight, subtle, gradual, etc, to be perceived. The word imperceptibility is derived from imperceptible, shown below.