In SEO, spam refers to any technique that violates search engine guidelines and/or provides a terrible user experience.
For example, doorway pages, page jacking, cloaking, purchased links and comment spam are all forms of SEO spam. All spam is black hat. A person or organisation who is guilty of spam is called a spammer – if SEO was a Hollywood film spammers would be the baddies.
Spamglish is the language of the spammers. It's basically keyword stuffed gobbledygook which makes absolutely no sense to a human and is an attempt by spammers to trick the search engines into ranking the page the nonsense is on high in the SERPs. Spamglish is often generated by machines which could generate pages hundreds of times faster than humans and threatened to replace our beautiful internet with gibberish. Thankfully, the good people who work at the search engines came up with better algorithms that can sort the Spamglish from the real, carefully crafted content.