Definition of "UI"

UI

noun
countable and uncountable, plural UIs
1. (Canada) Initialism of unemployment insurance.
2. (computing) Initialism of user interface.
  Quotations
  Some UIs tend to improve this by displaying toolbars only when they are related to any object manipulated (e.g., an image, a rectangle) and undisplaying them afterwards.
  2005, Maria Francesca Costabile, Fabio Paternò, Human-Computer Interaction – INTERACT 2005, page 199
3. (medicine) Initialism of urinary incontinence.