In a position of low priority. For example, I haven't forgotten his letter; I've just put it on a back burner for now. This term alludes to a cook's putting items requiring less attention at the back of the stove. [Colloquial; mid-1900s] Also see front burner.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.