custard pie

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A prop used in slapstick consisting of an open pie filled with custard or cream (or, more often nowadays, simply a paper plate covered with shaving foam or a similar substance) that is pushed into another person's face

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a prop consisting of an open pie filled with real or artificial custard; thrown in slapstick comedies