from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A state in which one thinks, especially carefully: put on one's thinking cap.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A metaphor for a piece of headgear worn while one is thinking about how to solve a problem.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a state in which one thinks
From considering cap (Wiktionary)