A dyke (or dike) in geology is a type of later vertical rock between older layers of rock. Technically, it is any geologic body which cuts across:1  flat wall rock structures, such as bedding. dyke (or dike) in geology is a type of later vertical rock between older layers of rock. Technically, it is any geologic body which cuts across: 1  flat wall rock structures, such as bedding.
Another example would be the âdefault browserâ on your computer. Windows PCs come with Internet Explorer (the blue âEâ icon) as the default browser, just as Apple includes their own Safari browser as the default on their Mac computers.
Mail is the default email app and Safari is the default web browser on your Mac. If you install other email apps or web browsers, you might want to set them to open when you click an email link or web link.