Dictionary.com
Thesaurus.com

jack rafter

American  

noun

  1. a rafter having less than the full length of the roof slope, as one meeting a hip or a valley.


jack rafter British  

noun

  1. a short rafter used in a hip roof

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of jack rafter

First recorded in 1750–60