To engage in so many activities that one can't perform any of them well: “Last semester, Pamela tried to play basketball, serve on the student council, and work at her father's store. She quickly discovered that she was spreading herself too thin.”
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Other Idioms and Phrases with spread oneself too thin
Overextend oneself, undertake too many different enterprises. For example, Tom's exhausted; what with work, volunteer activities, and social life he's spread himself too thin. This expression alludes to smearing something (like butter on bread) in such a thin layer that it does not cover the surface. Jonathan Swift used spread thin in a positive sense, that is, something should occur less often (Polite Conversation, 1731–1738): “They [polite speeches] ought to be husbanded better, and spread much thinner.”
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.