Definition's too wordy, tries to be too precise, and contains errors. All the OSR is is a bunch of people rebelling against modern D&D and often, by extension, other new games. What they in general reject is system-first game design.
Or, since you love to hate Ron Edwards, how about I explain it in terms that would enfuriate Ron Edwards? Ron hates D&D, Ron hates "simulationism". The OSR rejects the trend towards "gamist and narrativist priorities" in D&D and tries to restore simulationism. That's why Ronn made his recent dismissive comments about the OSR being just a marketing term. It galls him that people would want to fill blog posts with random tables of door types or monster motivations, or rant about the uselessness of game balance, or embrace "rulings, not rules" play styles.