Wipe, in a computing context, means  to render all data on a hard drive unreadable. The term is often used in reference to making data stored on a computer, smartphone or tablet inaccessible before disposing of the device.
A semantic HTML tag is one that defines a meaning to the enclosed content that a computer can be programmed to understand. In most cases, browsers create some visual difference to content in semantic tags, for example, content in the CODE element is usually displayed in a monospaced font. But this is not a requirement. Many people feel that semantic HTML elements are a waste of bandwidth.
What is the Semantic Web? Simply put, the Semantic Web is a more intelligent version of the web as we know it. Instead of just focusing on the structure of online data, it is more concerned with the semantics (i.e., meaning) of such data and how they relate to one another, as provided by descriptions and context clues that a machine such as a web crawler can read.