A long-winded lecture by anyone whose name starts with a B. This lecture will usually start off with the intent of answering a 'simple' question, or explanation. The person on the receiving end is usually a captive listener either talking to their boss, parent, or other authority figure.
Ironically, as long-winded as this definition is it also can be classified as a blecture if the person publishing it had a name starting with the letter B.
Tom: My boss just spent the last three hours explaining what our company's plan is for the new fiscal year when I just asked about our next meeting.
Mark: Sounds like you've experienced your first blecture