MBBB: McK, BCG, Bain, BoozMBB: McK, BCG, BainTop Tier: often synonymous with MBB (but people will differ)Second Tier: Could mean anything, from the Big 4 Accounting Firms to people like PA to strat firms like Marakon/LEK. Usually a bit meaningless unless it is clear in the post the type of consulting (Strat, IT etc) being talked about. Even then, people can argue ad infinitum about so-called 'tiers'.Blue-Chip - standard business term, look it up