from The American Heritage® Dictionary of the English Language, 4th Edition
- n.pl. Shorts or briefs worn as an undergarment, especially those for a man; underpants.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Underpants, type of underwear worn in skin contact with the hip portion of the body, small enough to be worn invisibly under shorts.
under- + shorts, by analogy with underpants, etc. (Wiktionary)