from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Lasting through the whole day.
- adv. Through the day; all day.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Which lasts a day, or approximately so.
- adv. Throughout the day.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. lasting through an entire day
- adv. during the entire day
day + -long (Wiktionary)