The phrase "visible lag" refers to a noticeable delay or pause in the display or response of something, usually a digital device or system. Full definition
On the performance front, there were visible lags while opening apps as well as switching between app. (indianexpress.com)
However, I encountered visible lags while multitasking as well as switching between tabs. (indianexpress.com)
Watch as a PlayStation Vita uses PlayStation Suite to (somehow) run Left 4 Dead on a PC, while displaying and controlling the game on a Vita with almost no visible lag - and even featuring optional motion control. (gamesradar.com)