See: Oversubscribed. When you subscribe to an offering, you sign up to buy shares or units at a given price. When you have the privilege of doing so, it means you're on the hook for buying those extra units if they get put to you. In hot IPOs this dynamism happens often. An IPO might be hyped and over subscribed to for weeks ahead of the offering, only to have demand fizzle just at the very end and when you had the "privilege" of buying 100,000 shares which was 80,000 more than you really wanted well, guess what. You're now the proud owner of 100,000 shares you bought at $15, trading now for $11.80. Ouch.