Crustard-top Share definition Flag Crustard-top - (noun) disc shape crust formation that forms at the top of a mustard dispenser. I've been saving up crustard-tops for 2 years. Pretty soon I'll be able to make a crustard-top sandwich. Crustard-top by Helmut Kientz January 21, 2007 0 0 Get merch Get the Crustard-top mug. Buy Now — $32.95 See more merch