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.
The <dfn> Tag in HTML 5. The <dfn> tag encloses the defining instance of a term in HTML. The dfn element is one of the phrase elements in HTML. The defining instance is often the first use of the term, and is found in the same paragraph or list item along with the definition of the term. The term that is being defined should be coded inside the <dfn> tag and can be any one of the following: