"Golden Horseshoe" means: The U-shaped area of the Canadian province of Ontario which extends along the northwestern, western, and southwestern shoreline of Lake Onta.... This is informal slang, common in casual speech, texting and social media, but not appropriate for school work, applications or professional settings. There is no real cause for concern in itself; it is everyday peer vocabulary. If your child uses it, a light comment about audience and register is usually enough — no need to escalate. Context, more than the word, tells you whether to follow up.