from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An acquired behavior or trait that is so long practiced as to seem innate.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A mindset, skill, or type of behavior so ingrained through habit or practice that it seems natural, automatic, or without a basis in conscious thought.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. acquired behavior that is practiced so long it seems innate
From the proverb Habit is second nature.(American Heritage® Dictionary of the English Language, Fourth Edition)