a user interface based on graphics (icons and pictures and menus) instead of text; uses a mouse as well as a keyboard as an input device
"The new software runs on a graphical user interface that allows me to navigate using both the mouse and the keyboard."
Initialism of graphical user interface.
"The company's new software update features a modern gui that makes navigation much easier for users."
In plain English: A GUI is an on-screen interface that lets you control software by clicking buttons and icons instead of typing commands.
"I left my gui on the table while I went to get some water."