"Noticeable lag" means that there is a delay or slow response that you can easily see or feel.
Sentences with «noticeable lag»
What brings it down is the cluttered interface and noticeable lag in performing certain tasks (in spite of a powerful octa - core processor). (techtree.com)
I see noticeable lag when pulling down the notification bar. (carrypad.com)
There's noticeable lag between hitting the accelerator pedal and the gearbox deciding to engage. (motoring.com.au)