1. in a manner that is impossible or very difficult to perceive, distinguish, or detect
Usage: formal; often used in philosophical or technical contexts

Examples

• The temperature rose indiscernibly over the course of the hour.
• The two shades of blue were indiscernibly different to the naked eye.
• The changes in the patient's condition were indiscernibly gradual.
• The sound faded indiscernibly into silence.
• The line between day and night shifts indiscernibly at dusk.