Entry: frustrum (n.)
In context: "Hal puts one foot up on Pemulis's little frustrum-shaped bedside stool and leans farther in."
Definition: The portion of a regular solid left after cutting off the upper part by a plane parallel to the base; or the portion intercepted between two planes, either parallel or inclined to each other.
Other: I was thinking that words with two U's might be rare, but they're really not. In Scrabble there are 12 words with four!
SNOOT score: 1
Source: Oxford English Dictionary