What is the X in X-mas?

# frustum

[fruhs-tuh m] /ˈfrʌs təm/
noun, plural frustums, frusta
[fruhs-tuh] /ˈfrʌs tə/ (Show IPA).
Geometry
1.
the part of a conical solid left after cutting off a top portion with a plane parallel to the base.
2.
the part of a solid, as a cone or pyramid, between two usually parallel cutting planes.
Origin
1650-1660
1650-60; < Latin: piece, bit; probably akin to Old Irish brúid (he) breaks, Old English brȳsan to crush
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source
Examples from the web for frustum
• The bore-hole is not a true cylinder, but the frustum of an elongated cone.
• Both these factors the form of a frustum of a paraboloid, then the equations can affect displacement.
• The outer shell forms the hollow frustum of an octagonal pyramid while the inner one is the hollow frustum of a cone.
• The rod was at the axis of symmetry of the conic frustum.
British Dictionary definitions for frustum

## frustum

/ˈfrʌstəm/
noun (pl) -tums, -ta (-tə)
1.
(geometry)
1. the part of a solid, such as a cone or pyramid, contained between the base and a plane parallel to the base that intersects the solid
2. the part of such a solid contained between two parallel planes intersecting the solid
2.
(architect) a single drum of a column or a single stone used to construct a pier
Word Origin
C17: from Latin: piece; probably related to Old English brӯsan to crush, bruise
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Cite This Source
Word Origin and History for frustum
n.

1650s, from Latin frustum "piece broken off," from PIE *bhrus-to-, from root *bhreu- "to cut, break up."

Online Etymology Dictionary, © 2010 Douglas Harper
Cite This Source

### Difficulty index for frustum

Few English speakers likely know this word

### Word Value for frustum

12
15
Scrabble Words With Friends